: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps



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BlueMoon
02-21-05, 04:59 AM
High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps...Seems too frequent not to be an eyebrow-raiser.

Let me start out by saying that I'm the proud owner now of a 96 ETC with the N*. I Love the car, it's looks, it's power and am impressed by the overall engineering of everything on the vehicle Except for one thing... the cooling system. I've noticed firsthand and reading on here thru countless posts that it's "typical" for temps during normal driving to cycle between around 190 to 230(some have even reported up to 250). I may be an "old school" wrench but even as much as technology has changed over the past few years, I am Not surprised that blown head gaskets and high oil consumption are mentioned so frequently.

Over the years it has become a well known fact that aluminum engines are more heat critical. Me, I like to keep my vehicles nice and in excellent working condition(and for a long time). This is why all of this is so bothersome. In the twenty-some odd years of GMs I've owned they've all had stable running engine temps and... I've religiously changed all my stock 195 thermostats out for 180's. I'm sure I'm gonna spark some heated debates here on that subject(and it is Not the subject I'm aiming to drum up some friendly discussion on) but it has worked VERY well for me over the years. I myself wrench and my past experience with this keeps gaskets from getting brittle and losing their seal, oil lubrication qualities high and better power and fuel economy from less detonation. The big thing to me is the longevity. In the many vehicles I've owned I've Never had Any internal mechanical failure, leaks or even oil consumption problems Ever. I've Never had any emissions passing problems either(Except for 2 of my 170,000 + mile vehicles needed a new cat as the pellet type just plain wore out.) I keep my vehicles for a long time and I also like to drive them "hard" from time to time too. So call it just good luck if you want.

Getting back to the subject of my post...
230+ running temp is too high for my liking(that's just my personal opinion). Sure maybe gasket and oil technology has changed over the last few years but that's just plain cooking hot in my book. Rings gummed up with "coked" oil... I'm not surprised. Early & excessive oil consumption...I'm also not surprised. Failing gaskets...you don't say. Just think how much even more heat your engine sees with heat soak(after turning the car off). Also not to mention you'd Never make it home having to put just plain old water in your cooling system from way out in the boondocks after say a hose failure. But OK. Lets just say "normal" it is per GM. What my bother is mostly about is in the stop and go temp fluctuations of this car. Think of it this way... if the aluminum of the engine is constantly changing from 190 to 230 as you idle then drive: 230 - 190 = 40 degrees of CONTINUAL temp fluctuation. If you don't think that's a big deal drop a 30 degree ice cube into a 70 degree glass of soda....but Keep doing it. Sure that's kind of an extreme comparison but that much of a continuous "Swing" CAN'T be good for the expansion of an aluminum engine held together with steel bolts. Bars leak or not, it just seems like a problem waiting to happen from a machinists and a mechanics standpoint. All of my past vehicles had stable operating temps, why not this one I've been asking myself...

So in I jump under my hood... replacing the thermostat(from the dealer), checking the water pump, belt and tensioner, pulling the radiator and inspecting the tanks & tubes, changing the hoses and ultimately the coolant(after a good flush). Everything is A+. Even the coolant lines, restrictors and the heater core all flow well. Still I get temps all over the place(190-229). That's even in the cold Chicago weather here. My fans are functioning(kick on LOW at 225), but still even with the vehicle moving in very cold airflow it's still all over the place. Definitely not stable.

Can someone tell me... am I seeing things or is the thermostat mounted on the coolant RETURN side INTO the block?(cooled water coming FROM the radiator flows thru the thermostat???) Please tell me that's NOT so!

(Unless there's something wrong with my eyesight it looks like the RETURN line from the heater core is the only thing that heats the thermostat up to open. And that would be mixed with the cooled water coming from the radiator too!)

BeelzeBob
02-21-05, 02:37 PM
I understand your thinking and line of thought....but....it really isn't correct.

Coolant temps in the range of 230 are perfectly normal and desireable.

As long as the engine is "wet" and full of coolant that is circulating it will not be damaged and can run as hot as 270 degrees or hotter for EXTENDED periods of time without hurting a thing.

A system that has a 50/50 mix of ethylene-glycol coolant/distilled water and is pressurized to 15 PSI (normal OEM cap) will not boil until 265 degrees.

There is little to no correlation to ring belt deposits and coolant operating temperature.

There are millions of Northstar engines on the road that operate perfectly fine at those operating temperatures. You read about a few problems on this and other forums....but...forums are like that. Everyone with a problem looks up a forum for help/information/commiseration/venting...but few look up a forum to brag about their Northstar with 200K miles on it....

I have seen MANY endurance and durability engines that ran 100K miles of heavy duty use in the Phoenix (GM Desert Proving Grounds) area and off property in the hills and grades of the desert south west. Those engines LIVED at high coolant temps all their lives and they look fine inside. Better, in fact, than engines running "cool" in cold climates.

I have personally run many high speed endurance engines on dyno test (full power, 6000 RPM, 300 hours) at elevated coolant levels and the engines just do not care if the coolant is at 210 or 250 or 180...... They hotter they run the better they look, actually.

Based on your observations of the coolant temp in your 96 ETC I would ask...is this your first experience with a FWD car with electric cooling fans..?? I suspect from what you say it may be as the temperature excursions you observe are more a function of electric cooling fans than anything else. Electric fan cooled cars typically have fairly regular coolant temp excursions due to the lack of air flow thru the radiator when the car is not moving. Older cars with longitudinal engines (typical RWD) had engine mounted fans that always pulled some air thru the radiator. Cars with electric fans have NO airflow at low speeds and idle so the coolant temp naturally creeps up...until the fans turn on...then the temps go back down.

You will notice this much more in the winter and cool weather than in the summer. In the summer, when the AC is on the fans will run most all the time due to the requirement for constant airflow over the condensor for the AC. The AC system has almost no thermal inertia unlike the engine cooling system therefore it needs the constant air flow. When the fans are running due to AC requirements they provide radiator airflow by default so the coolant will stabilize more at the stat temp. In ambients below about 40 degrees the AC compressor is disabled (or when you drive on ECON or OFF) so the fans only run when the coolant gets to 225F. That is perfectly fine and is as designed. Seems odd at first to notice more coolant temp swings at colder ambients but that is the nature of the beast with electric cooling fans.

Putting a lower temperature stat in the engine is counterproductive to the engine control system as many coolant thresholds in the calibration are based on the operating temp of a 195 stat (which usually controls around 205-210 in the engine) as designed AND the stat control temp is closer to the fan turnon temp of 225 F Coolant so as to minimize the amount of temperture cycling of the engine. Putting a colder stat in increases the amount of cycling that you are observing as the engine will cool down to the lower stat temp when moving/fans on and then heat back up to the 225 fan on temp when idling/city traffic.

It is desireable to get the coolant above 212 F so as to heat the oil above 212 in city driving quickly so as to boil out moisture and raw fuel that gets in the oil on cold starts. Running colder thermostats is detrimental to engine life from this aspect, particularily in colder climates and in short trip/urban driving that doesn't heat the oil up otherwise.

The Northstar cooling system is a very sophisticated, high flow system that is designed for a high output, high RPM, all aluminum engine...not a system that was adapted from an older, slower turning, cast iron, low output engine. The water pump on your 96 will pump around 105 gallons per minute at 6500 RPM (that is TWO 55 gallon drums in 60 seconds....think about it) while requiring a minimum of power to do it. It is a very efficient water pump impeller design that is designed to turn high RPM and move a lot of water.

The main consideration of an all aluminum engine is NOT the absolute coolant temps observed but maintaining thermal stability throughout the engine. Keeping the hot spots cool and the cool spots hot eliminates thermal fatigue of gaskets and seals and allows the engine to "grow" and "shrink" with coolant temp changes as a single entity...not dissimilar parts that stress the fasteners and gaskets. This is accomplished by having VERY HIGH coolant flow rates thru the block and heads constantly so as to maintain an even temperature gradient across the engine regardless of the observed coolant temp.

Keeping in mind that the water pump can pump about 105 GPM at 6500.....only about 45 GPM is directed to the radiator. That is sufficient for the heat rejection required and is the maximum that is allowable for the long term life of the radiator....erosion of the tubes, tanks, and end-tank oil coolers would result with more flow. So....where does the other 60 GPM go....???....it is recirculate back thru the block and heads in a re-circulation loop....part of which is the heater core circuit which accounts for about 7 GPM of flow at maximum engine RPM. The main part of the recirculation circuit is the cast passages inside the water crossover casting that the water pump resides in. When you remove the stat you can see one of the coolant bypass passages at the end of the thermostat mounting port...the large hole that the spring loaded paddle covers.

The inlet thermostat design is used to minimize the efficiency of the water pump and to limit thermostat induced temperature cycling in colder weather. The stat has many functions. The spring loaded paddle at the end closes off the bypass port (the bypass that bypasses that 60 GPM back thru the heads and block) until sufficient coolant pressure blows it off and establishes flow. Under normal conditions the temperature sensing element is bathed in the bypass flow consisting of the direct bypass port, the heater core circute and "cold" water that is being admitted by the thermostat. This lets the stat see a true operating temp of the engine as opposed to a more conventional exit side stat that only sees coolant temp when it opens and coolant is flowing past. Nothing wrong with your eyesight....you just have to dig into the engine and the passages in the castings to understand the cooling flow path...or get a service manual and it is spelled out very clearly in a nice diagram for you.

The water pump in the Northstar is prone to "vapor lock" if it injests any air bubbles so the water pump cavity is continuously bled or air or bubbles thru the vapor vent line that is the 3/8 hose leading from beside the upper radiator hose to the pressurized surge tank.

The system uses a pressurized surge tank as the high point of the system so as to de-aireate the coolant in a quiet, low flow area, allow for expansion and contraction of the coolant, provide a means of real time low coolant level warning BEFORE it impacts cooling capacity, and, primarily, provide a source of clear, pressurized coolant directly to the water pump inlet port to prevent the pump from cavitating in high demand situations. The heater core circuit exits the water crossover casting after the coolant traverses the block/heads and returns thru the circuit from the pressurized surge tank to complete the circuit and supply a constant feed of fully pressurized coolant to the water pump inlet where the negative pressure would be the greatest and cause cavitation.


Before you start redesigning or re-engineering the cooling sytsem on the Northstar engine you really need to understand how it works, why it is designed the way it is and what the impact of your design changes are. There are thousands of hours of development time in the cooling system of the Northstar and the vehicles it is installed in. It was not taken lightly, trust me. Basically, it serves as a very good example of a high performance cooling system for a high out put engine. There is nothing that was compromised on the cooling system design and the design features pioneered on that system in 1993 have been incorporated in other high performance cooling systems throughout the automotive industry....i.e...pressurized surge tanks, vapor vent lines and continuous air bleed systems, inlet side thermostats, high bypass ratio cooling porting, very high flow water pumps, etc....


BAsically, every thing you did is perfect to make sure the system is in top operating condition. The one thing you did not mention is the addition of the GM Coolant Supplement pellets to the system to guard against any incidental leaks from porosity in one of the aluminum castings or a gasket imperfection. It is designated as a required item in the cooling system. Search the archives using "coolant supplement" as a topic and read my posts for more info on this as much has already been posted.

You are, however, trying to fix something that is NOT broke. Put the OEM stat back in as that is what is best for the car and engine. It will actually reduce the level of coolant temp swings you are seeing in cold weather, will warm the engine to the temperatures the clearances were set up for, will match the PCM calibration set points for coolant temperature and it will improve the oil life and oil quality particularily in cold weather. Keep the system full of 50/50 Texaco DexCool/distilled water and install the 6 coolant supplement pellets into one of the radiator hoses....not the surge tank.


YOu make a good point about the thermal distress that can be caused by continual coolant temp changes...to a degree this is a concern and something that the engine developement engineers take into account. Thermal fatigue of gaskets and such is what it is called. The problem or concern is mitigated, however, by the very high flow rate of coolant thru the engine, the high rate of coolant bypass that is already heated by the engine and is simply bypassed to stabilize the internal temps and the higher operating range of the OEM stat that more closely matches the coolant temp that the electric fans engage at. Lowering that stat temp with a "180" stat makes the situation WORSE not better. The thermal fatigue issue of the gaskets and engine internally is also mitigated by the fact that the WHOLE engine structure changes at once due to the high coolant flow rates. If the parts all grow and move and shrink TOGETHER then there is minimal fatigue of the gaskets and such. This is one reason the engine lasts as well as it does in fact. Most all of the head gasket problems and such mentioned on this forum are on engines that have well over 100K on them...unheard of 20 years ago. Furthermore, when dissassembled for repair, the engine look like new inside with nothing other than head gaskets and (occasionally) a head bolt thread repair. If the cooling system was not working correctly on an all aluminum engine that turns 6500 regularily and makes over 1 HP per cubic inch it would fail MUCH sooner.

blunted
02-22-05, 09:39 PM
That was another very good thorough explanation.. someone add it to Bbob's memoirs! Make's you happy to own a caddy , and shows the true strong points of these cars and their design which people forget to acknowledge in the middle of them only stressing it's shortcomings. I know one thing, this is the only car I've owned and been in that has been complimented so much, even once by a guy driving a brand new S600 while smoking his imported cigar.. he was very impressed how the caddy sounded with its mufflers and the way it moved. :coolgleam Gotta love dem caddys!

BlueMoon
02-23-05, 01:10 AM
I have to disagree with you on a few things.
Yes, on a dyno hotter is better. That is true in terms of combusion temps and EGT. It
correlates to thermal efficiency. But I'm speaking in terms of block temperature. I have "some" experience in dyno use in R & D. And higher block/cylinder head temps cause preignition and detonation. That in turn causes lower efficiency and lower power output. Especially in motors that are running higher compression(like todays production cars). Their higher compression "plus's" can't be used. Take a look at when the knock sensors are most commonly cutting back timing... it's when the engine is it's hottest. It's more complicated than that, but that's a simple example. In engine design there's always one good characteristic trait that you can increase while another works against it. But engineers are always searching for that happy balance.

Engines live "better" at higher temps??? Never from a wear and tear standpoint. Too hot or too cold is Bad.

Also, no matter how high a flow rate this cooling system has, yes higher flow Will help
eliminate hot-spots, but you're missing my point in all this...block temp swings and poor regulation(and thermostat location). I'm Not seeing this "thermal stability" you talk about.

The Northstar is a nice piece of work making more than the "covetted" one horsepower per cubic inch category. But that isn't hard to achieve these days with four valve per cyclinder motors and fuel injection. Even on pump gas. The efficiency of 4 bangers has come to that over the years as they are now making as much power as the V8s of 10 years ago. And they're getting good gas mileage too. But these little everyday 4 cylinders are seeing far more of a duty cycle than the Northstar. The N*s power is rarely even exercised in even aggressive everyday driving. So these motors should Really last. Yes, I know there are millions of them that have not and will not ever have a problem. But we're now getting to the times of warranties lapsing and people buying more of these cars second-hand and working on them themselves. So you're really beginning to see what's going on and what's frequent to happen(as in this wonderful board. My hat's off to all of those sharing their experiences to make life a little easier and "richer" for others). I am not new to engine design and development but I Am new to the Northstar community. It's also seemingly "popular" that if you ask any mechanic what the "weak point" of the N*'s is and what they've commonly seen
thru the past few years, guess what they're gonna say???? :) Yes, you guessed it...head gaskets. But, it seems most of them will say it's the Dexcool that caused it. On the flipside there's my point on the temps being all over the place and High. Me, I don't see anything wrong with dexcool. I also don't see anything wrong with the design of the mating surfaces or the gaskets or the bolt threads themselves either so far.

Your reasoning for design of that high of a block temp doesn't make sense in terms of
boiling the moisture and deposits out of the oil. Not in that extreme of a measure is what I'm saying. Yes, it is necessary to bring oil temps up to evaporate moisture and some of the other by-products of combustion that get past the rings ...and to attain the desired "fluidity" to create the desired film of oil(to put it in the simplest of terms). But too high of temps will prematurely accelerate the breakdown of the oil and it's desired characteristics. Part of the reason we change our oil is because it becomes contaminated and part is because it's decomposing and losing it's lubrication qualities. And heat accelerates this decomposing process. Not to mention too high of heat Will leave coke-like deposits(sludge) earlier than normal because the oil Really starts to breakdown. The rings and pistons sre one of the hottest parts in an engine. So, Yes and No. You are correct in that the piston and ring temps don't have much to do with coolant temps. They are primarily cooled by the oil. But technically by having the whole "assembly" say 50 degrees hotter just "steps" everything up. I personally don't see this motor not having oil consumption issues starting at even 10K miles without the high oil capacity and oil cooler setup it has. It is Very much needed with this motor in it's "common" temperature range(s).

Some of the other possible reasons for high block temps that you have not mentioned are increased passenger compartment heating and lower emissions. I could possibly see GM's R & D going for the emissions standpoint, but with today's self-heated O2 sensors and close-knit computer control, the emissions are already very well regulated.

Yes, I have also had experience in FWD cars and electric fan setups. I'm Very familiar with them. There Is a typical cycling range the fans will keep things in "check" between. But, I've Never come across such a wide range before. I'm trying to keep the subject on the thermostat for the moment. Fans are fans, they do their job depending on when you turn them on and off. I'm talking about the poor engine temp regulation when the car is at 35 MPH + in 30 degree weather(forgetting about the fans). You can wire the fans on HIGH all the time when it's cold out and the block temp is Still all over the place.

Getting back to my thermostat topic...
I did some more looking into the placement of the thermostat and it IS as I had suspected. So I am now not surprised with the behavioral characteristics of this car's cooling system. I think I'm even more bothered now than before too. If cooled coolant is flowing thru that thermostat, it's Gonna keep cooling/closing itself making wide swings and cycling. The thermostat in this setup is "fighting" itself.

Then, I see there being a "runaway" point with this setup. A point where the demand for cooled water by the engine won't be met because the higher amount of cooled water flowing thru the thermostat will cool and close itself... yielding a condition kind of like a reactor going out of control. I can see now why there is a "Limp Mode" initiated by the computer. There HAS TO BE! Let me tell you something... you will NEVER see me "putt-ing" along down the road with no coolant in my motor impressed as all hell that this "baby" is still running and some hot dog engineers are "wise" enough to turn off some of the injectors to keep it from completely seizing up. A motor ran at 260-270 IS SHOT. It'll only be a matter of time. The resiliency of the head gaskets is GONE, the heads Will expand and distort as the bolts try and hold them down(or strip/pull out) and most importantly, the piston to bore clearance will Disappear and the pistons will gouge and distort the bores of the cyclinders. It'll be Guaranteed to burn oil And lose a headgasket or two eventually. I have firsthand exposure to motors seeing those temps and what the piston skirts and cyclinder bores look like at those temps.... SHOT. The N* may have some advanced engineering
to some in it, but some space-aged aluminum, steel and gasket materials with abnormal physical properties I Don't see it having. Also, unless these motors are machined out of the factory with larger than "typical" piston to bore clearance to sustain excessively high temps, I so far have not heard any piston "slap"(the piston rocking in the bore) on cold startup. (That is something I will be looking into later...ring end-gap and piston to bore settings of this motor)

NEVER in all my years have I seen a thermostat mounted on the COOLED/RETURN side of the block. WHY this setup I ask??? Was it engineering "hot-dogging" or just space constraints? I think I remember seeing something about the N* cooling system to be designed with increased passenger compartment heating in mind. That would explain the heater core return temp affecting/controlling the engine's running temp. This also explains why blocking off the heater core lines would cause overheating...the thermostat would Never warm up to open!

That little device called the thermostat for what little it costs does an Incredibly good
job of regulating engine temp when it's mounted to "see" the heated engine coolant. WHY "fight" something that's worked So Well over all these years???(and even today still with 99.9% of the vehicles on the road). So far I am Very UNimpressed with any hi-tech-ness to this cooling system. I see Nothing out of the ordinary other than cooled EGR feed ports and an unheard of wrong side thermostat installation. But hey, hat's off to some engineering "feats" to make it happen.

Car companies regularly give teams of employees a budget to take and use with their skills and creative imagination to produce a product that will catch the consumer's eye, sell cars, and ultimately make the company money. There are some tried and proven design aspects that are typically followed in research and development, but employees are Encouraged to use their imagination to come up with new and exciting designs and discoveries. Hundreds of millions of dollars is "played with" in this respect. These companies also have testing and endurance procedures in place to keep the R & D departments in "check" so that they're designing stuff that will last and are not just awe inspiring to make their bonus's. But these testing and endurance tracks and dynos can never fully achieve real world use as hard as they try. Still to this day ALL car companies still churn out cars that have design flaws. Things that fail prematurely. Some even bad enough to warrant a recall. It's something that will Forever continue to happen. CAD programs and test tracks will forever fall short of actual use. Period.

I am not trying to cause panic or tick off anyone with what I'm saying here. Nor am I
suggesting that there is some huge problem with this car as it rolled off the assembly line. I'm just saying I see things here that are Very different from the "norm" of other vehicles of even today. Everything is bound to eventually wear out/decompose/need service. Everything. Nothing lasts forever. But I see some uncommon characteristics here. Some that don't surprise me with the end results. I apologize for walking in here and sounding so bold being a newbie to this board. But another thing that's been raising an eyebrow to me is your "That's the way it is. Accept it." attitude bbob. It's as though you take every person's head gasket/oil consumption problem personally and tell them to just follow the repair procedure and live with it. Helpful, but oddly personal. For every problem there is a reason and a cause. So far I have seen No mention or plight for a cause other than an argument about dex-cool. I am the type of person that likes to nip things in the bud before problems happen. I like things to perform for me and with good peace of mind. And my reasons for posting are not to rip anyone or anything, but rather to inspire some healthy discussions to possibly make things/life better. We all want that I'm gonna venture to say. So I do appreciate your taking the time to comment back and type all that back.

You mention that I am just becoming alarmed to posts on this board as only seeing a select few people posting their failures. With other vehicles and their associated forums I've been on, typically the big/common topics are performance mods, Audio/Visual upgrades and neat mods/experiences. Random problems and fixes are always there and are just that...Random part failure. But once in awhile you will see a certain vehicle type with an inherent typical problem. Here, time and time again, the big subjects that keep popping up are Head Gaskets, High Oil Consumption and alarming coolant temps.

I could go on and on, but let me finish this long post with this...

Lingenfelter and many other high performance/high endurance engine developers have always pushed for lower block coolant temps. So please don't look at me like I have 3 heads. Cooler stats come in almost Every aftermarket mod these days. Even some of new cars coming out of the factory today are running < 195 block temps...And most importantly THEY RUN AT A STABLE TEMP.

I am expecting differing opinions and comments returned and that is more than fine, expected and encouraged. To this day different engineers will argue one tidbit till the death against each other(say intake port shape for example) and NEVER agree. Each of them spending tens of millions of dollars on R & D in their different companies and each of them coming up with different shapes and port sizes. They are set in their ways and both believe they have the BEST setup. My point is this... some things work better than others while both will work relatively fine. There are those that are ho-hum with the way things are and they accept things the way they are. And that's fine. But let me ask you this...How many of the owners on this board do you think drive around worrying about when/if they'll ever have to end up having to give timesert a call? Do you think that's not something in the back of people's minds? No peace of mind there. As I've said, All of these points I've made can be argued. But me stressing the importance of a stable running temp I Do have to stand up to. I would definitely like to see that in my Caddy. For those of you that Don't think that will increase the longevity of this motor...I'm very sorry you believe that.

P.S.: Just a little FYI: the OEM thermostat for these cars is a 180. But the engine hardly ever sees/stays at that. It's pretty obvious now why. I Definitely would NOT put an even lower degree thermostat in my engine. Temp swing is what my gripe is All about.

dkozloski
02-23-05, 02:29 AM
Pretty good rant but I think you're just a litle bit late. My '04 CTS with the VVT V6 North* has an analog temp gauge that never budges off the straight-up mid range mark from ambient of -49F to +95F over any terrain. What ever the problem may have been, has been designed out of the newer motors. At the same time the water temp my '95 Ford Ranger 3L V6 wanders all over the place for no apparent reason but with no apparent effect. The temps you make such a point about for North* motors are childs play. My copy of the pilots operating handbook for the North American F82 "Twin Mustang" with liquid cooled Allison V1710 engines lists the normal coolant range as 221F to 239F with 275F as the upper limit. The upper limit for cylinder head temps of air cooled aircraft engines are about 460F at the bayonet probe location. Pratt & Whitney R1830 engines have been operated with cylinder head temps in the low 70's F. and it isn't known if this is the lower limit. These engines were getting times of 3500hrs between overhauls when operated at these temps. That works out to about 700,000 miles. The point I am trying to make is that engine temps can be all over the lot for any number of reasons but what works, works. Much ado about nothing, a tempest in a teapot.

ZSKI
02-23-05, 12:45 PM
Maybe I am missing something here. My 1999 DeVille with 46k runs all the time (winter / summer) at 202 - 210 degrees F. Seems pretty stable to me!

blunted
02-23-05, 03:08 PM
Bluemoon : Personally I think there might be some kind of argument made to the effect of what you said but I do believe it's more of a "in theory" on paper kind of thing. Yes I'm sure you might find the set-up of the Northstars cooling a little on the "different" side but do not make it seem that this engines are designed in a way to self-destruct themselves. Many people own these cars with these engines that last a very long time, there is even a post in this section about one nearing 400K. That might not be the norm but these engines do survive with engineering put into them, my temps do jump around and have hit 234 while driving but that is as a NYC driver where this is stop and go and the fast acceleration to pass someone to then shortly come to a stop. Anytime I drive a constant speed in the country or highway the temperatures are not moving constantly until I come to a stop or close to it. As a 94 Eldorado owner.. YES the time-sert issue is on the mind to a degree but I have calmed down with that as well after looking at it from a different perspective. If you do what your supposed to with the cooling you should be ok, I havent heard many people saying their heads blew and that they've been the ones to responsibly maintain that cooling system for the life of the car. It is more like " I bought this car with 1XX,XXX miles and 20 thousand later I blew it" or something to that effect. My car I bought with 59K, and serviced the cooling system right after, to me this means that it came filled with fresh coolant that was good for around 30k or so and there's possibly 29K miles I have to perhaps wonder if the owner bothered servicing the system in. But hey, thats the risk you take and usually people do it while factoring in alot more "questionable" miles. So all these headgasket problems are more what people make of it in my opinion, which is just that.. MY opinion. If you go to the caddyinfo message boards you will see that they recently did a poll of how many people have needed headgaskets and when you see the number of high mileage northstars that are fine , maybe you will rest a little easier as I did. I think the best idea is to do what Bbob has told many people.. "shut your display off and drive the car", it's the great electronics in the car that let you monitor everything going on with it and it turns out to be its biggest enemy sometimes because thats all people do, monitor it and stress every degree that goes by. Also, on the topic of these vehicles consuming oil... YES they eat oil, live with it! So do many other high end automobiles that cost even more than a cadillac, if you wanted something that never ate oil or that you didn't want to worry about changing than why you dont have a Honda is beyond me. For all anyone knows their "reliable" cars might not have the most stable tempatures all the time either, but you wont know because it doesnt have a sophisticated computer in it telling you what's going on throughout the car at all times. Heck, I almost bought a V6 accord :cookoo: cause it was "reliable" but I saw the Eldorado and instantly fell in love and went with performance over reliability. Granted, I have put more money into this car than I would have needed with an Accord, but I would NEVER and will never trade that for the feel and power of this car.. Amen.

BeelzeBob
02-23-05, 04:13 PM
bluemoon....I think you are misunderstanding part of my post. The answer to much of what your second rant addresses is in my first post.

Look at the Northstar thermostat carefully. The thermostat element is "seeing" the bypass coolant primarily which is the true temp of what is in the engine. It is not just seeing the "cold" coolant coming in. The cold coolant into the engine must mix with the high bypass flow before the stat thermostat element sees it...so...the stat is seeing what the engine is going to get for coolant temp. Exactly what you (and the engine) want it to.

Be carefull of what "Lingenfelter" wants and what works on the dragstrip for instantaneous power for a burst reading. Passenger car engines are designed to operate under a hugely wide variety of conditions....not just make power down the dragstrip or pull a big number on the chassis dyno. You are not going to see Lingenfelter's or anyone's hot rodded engines make the kind of long term durability and endurance of the production engines. Cool stats are admittedly "good" for power for burst readings and helping with detonation. But passenger car engines must also have PCV systems that work, pass emissions that are far more stringent than sticking a probe up the tailpipe for 2 minutes, cool pulling trailers and heavy loads, work in -40 weather going to the store as well as idle in Phoenix city traffic at 120 ambient. What "Lingenfelter" or other tuners expose rarely meets the requirements of the general population.

I agree that very high coolant temps can aggravate detonation and preignition tendencies....but....that is at the far reaches of the elevated coolant temps. We often talk about what the highest temps can be and how hot can it get without hurting anything, etc....but.....most of the cars most of the time run around the 210 range very repeatably. The excursions to the very high side simply are the far reaches of the systems capabilities...not what most people experience most of the time. Yes, the knock sensors will start to pull spark out when the engine reaches 250 and 260 degrees to prevent detonation....but.....the compression ratio and spark advance was carefully optimized to allow operation at MBT spark (optimum spark advance for power and torque) AT THE COOLANT TEMP RANGES NORMALLY SEEN. In other words, the engine will operate with no knock sensor induced spark retard at 210-225 with no problems at all. IT WAS DESIGNED TO DO THAT. And it was tested and calibrated under those conditions to make sure that it will. If not, the compression would have been reduced. There is FAR FAR more to optimizing these packages than the one dyno pull you read about in Hot Rod magazine!!


I do understand your comments about the coolant temperature swings and the damaging effects....I thought I addressed that in great length in my post. The swings can have a deleterious effect if they are not controlled and if the engine is 'seeing" the shock of a coolant temp swing suddenly. This is mitigated , as stated above, by the high flow rate system and the huge bypass flow that mixes with the incoming coolant to keep the engine at ONE temperature and to allow it to change as one piece due to the high coolant rates flushing thru it. It warms the cold spots up rapidly and cools the hot spots rapidly so as the keep the engine globally at an even temperature and allow it to globally change temp as one entity.

GM does extensive "thermal shock" testing of the engines by flushing hot (very hot...like 258 degrees F) and cold (very cold...like -20 degrees F) coolant thru the engines to "work" or distress the gaskets as much as possible to accelerate failure modes for testing purposes. The Northstar engine excells at this type of testing due to the high coolant flow rates forcing the global temp of the engine to change as a single entity rather than part of it gettting hot and part being cold...or vice versa. I do this type of testing regularily so I see the results constantly and the Northstar does very very well at it.

Things are different on the engine...?????.....uhh....welll....uhh.....yea. It is all aluminum, it does make a lot of power and rev hard, it doesn't have pushrods, etc..... Things do change. Look under the hood of any GM car and the competition and things are not llike they used to be. That is a good thing. Not something to bemoan.

Inlet side stats a poor or questionable design....??? They are very common these days on modern engines. Look around. They are not an engineering exercise. They are done because they do a better job of modulating the coolant temp than exit side stats do despite your theories to the contrary.

Realize that you may not be "used to" temperature swings but many of the temp gauges that you have used over the years are very "dead" around the 200 degree operation point so that you just do not see the coolant temp swing. The gauges are damped (deliberately) to prevent the customer from worrying everytime it moved. Sounds like you need a damped gauge. Your 96 is a particularily active gauge and digital readout due to the desire to provide accurate and instantaneous information. Generated lots of complaints because many customers (like you) get worried if the gauge moves one needle width off center or wags around at all. Later model Cadillacs have the coolant temp gauges and digital readouts "damped" considerably to prevent this issue......true.

You are missing the point I made earlier...... by lowering the thermostat operating point you have INCREASED the range and likelyhood of the coolant temp swings that are seen. You have made the situation worse with the colder stat. That is your fault, not Cadillac or GM or the engineers that designed the system... Normally the upper end of the temp range (in normal, 99 percentile conditions) is dictated by the fan turnon point and the lower end by the thermostat control point. If the thermostat active control point is 210 or so and the fans turn on at 225 then it is onlyl 15 degrees. Put a 180 stat in there and the coolant will cool down to 180-190 with the fans on and then warm up to 225 when they turn off. NOw you have created a 35 or 45 degree range. PUT THE OEM STAT BACK IN. It is designed for the system to operate that way. I can commiserate if you want to change it for change sake....but....since you cannot reprogram the fan control point you really need to let the sytem work like it was designed....not like your misguided , preconceived notions dictate. Realize that the engine and cooling system was optimized for a variety of conditions and to operate at the most efficient point for the engine. It was NOT designed for you to be able to modify it easily...or at all. Aftermarket modifications to the sytem are not something that the engineers even consider. So, if it is hard to modify like you want......tough. That was not one of the design constraints.

Trust me, there are a lot of pretty smart engine cooling engineers and developement engineers working on those packages. And, as stated, the Northstar engine received tremendous attention to the cooling system by those engineers. Regardless of your background, you have some catching up to do to understand how the sytem operates and what needs to be done to "improve" it.


AS far as engines living better when hot....I see the examples daily from the factory testing. I know that they live better running the higher coolant temps. And I see the results from the field of running the higher coolant temps of todays engines. The engines look much better and live much longer and have far far fewer crankcase oil deposits and problems of that type. As far as oil oxidizing at higher coolant temps....cold coolant temps are as deleterious to oil more than higher temps. Getting the coolant above 212 boils off the junk sooner in short trips which the general public does frequently. Oil oxidzes severely and becomes a concern above 305 degrees F......far far above the coolant temps that we are talking about.

Talk about another misconception....most people think oil is supposed to NEVER get above 200.....LOL......we always want to see the oil at 230-240 to keep the water and heavy end hydrocarbons boiled out of it and to improve the fuel economy. Modern oil is MADE to run at those temps. You are not helping it or the engine by keeping it colder.


I just believe that you are so firmly convinced that you have discovered a major design problem here that you cannot see what it really going on the system. It does work well. It works better than systems of the past and, as indicated, pioneered many items that improve the performance of cooling sytems that are seen on other cars today. It is designed to operate at higher coolant temps for longer engine life (in the real world from Fairbanks Alaska to Death Valley, Calilfornia) and it does it quite well as long as it is maintained and not modified. Don't blame the system for poorer perceived operation due to your colder stat mod.


The bottom line is that if you read thru posts on the previous pages you will find pictures of Northstar engines torn down with nearly 200K on them. The pistons look great. The cylinder walls have the original facotry honing marks in them. The valve seats and heads are perfectly fine. Timing chains and sprockets and cams are perfect. etc..... Not bad for an engine that the engineers botched the cooling system on I would say.

Yes head gaskets rise to the top of the most common failures as the engines age. For 150k to replace the head gaskets and drive another 150K is pretty good I would say. Compared to the "old days" where engines needed rebuilding at 100K and the cylinders had such a ridge at the top that you couldn't get the pistons out the Northstar lives and wears pretty well I would say. Every engine has maintenance of some sort required as miles build up. Seems the Northstar needs an occosional head gasket. Lexus engines need timing belts. Cost is the same. Break a timing belt and you buy a new engine. Loose the head gasket and you get plenty of warning, it is easily repairable and the engine requires no other work.


By the way.....you are completely off the mark with the idea that the cooling sytem can "run away" at some point. And the idea that an engine that is run at 260 - 270 being shot is ludicrous. Completely ludicrous. I have seen many many engines run to those temps during testing...some for extended periods of time (like as in hours) and they are fine. As long as the engine has coolant in it and it wetted it is fine. Your idea of what is going to cause a failure is not reality. Having worked on the developement of the limp home mode I do take a bit of offense to the cheap shots you take at it. The engineers realized early on that an all aluminum engine was going to be very susceptable to damage if overheated severely so the limp home mode of cutting out cylinders to allow the engine to "self cool" was invented and developed. There was one Northstar engine that spent a solid 10 months on a dyno developing that system to the point that a Northstar can literally run with NO COOLANT IN THE SYSTEM for 50 miles at 50 miles an hour to allow the customer to reach a safe spot in the event of a system failure. It works. I have left work with a "dry" Northstar many times, driven 40 miles home, parked and went into the house, started the car the next morning and drove 40 miles back to work....with no coolant. The engines run fine when filled with coolant afterwards. This has been documented by several major santioning organizations and by two separate magazines that ran their own "validation" tests (one by driving from Yuma to San Diego with no coolant) to prove us wrong and in the process wrote excellent testimonials to the success of the system.

dkozloski
02-24-05, 02:55 AM
Among engineering professionals, GM engineers are regarded as being the finest automotive engineers in the world. They have pioneered virtually every device commonly available on cars worldwide today. From the self starter, to Ethyl gasoline, to power steering, to automatic transmissions, to recirculating-ball screw actuators. The list goes on and on. The idea that someone is going to reverse engineer and reinvent the cooling system of a North* by peeping in the holes with a flashlight is pretty far fetched. If Bbob tells me how and why it works like it does I am ready to believe him and go on to the next issue.

dkozloski
02-24-05, 03:25 AM
GM engineers are not all gods however. Chevrolet had developed an automatic transmission for Jim Hall to use in his Chaparral sports cars. This gave a free foot to the driver that Hall took advantage of to control a huge wing on the back of the car. The car was unbeatable. Ford wanted a comparable transmission the worst way and decided to hire the responsible engineer away from Chevrolet. Chevy management got wind of this and cooked up a practical joke. They leaked the name out of the supposed engineer but in fact it was a dud that they were ready to can for incompetance. Ford hired the guy and put him to work leading the design team. The resulting transmission was put in a Ford GT40 variant called the "J" car. At 220MPH the transmission seized up resulting in the death of Ken Miles, one of the finest race drivers of the times. In the end the Chevy transmission turned out to be a beefed up "peanut butter drive" Powerglide.

BlueMoon
02-24-05, 12:59 PM
I don't believe I was taking pot-shots. I was just stating some very visible aspects of this cooling system and looking to spark some thought into better longevity of this engine.

My background is NOT a Hot Rod magazine reader. That I found to be an outright insult. Especially since you don't know who I am or where I'm coming from. I'm guessing you took that assumption from the Lingenfelter example. But it was just that... an example(of many). As I stated in my above post the BIG 3 at this moment are rolling cars out that have <195 running temps. So I wasn't just talking about ONE guy doing something in my previous post.

If you wanna talk about Lingenfelter, he doesn't do just burst and dyno run research. And he IS involved with passenger vehicles and endurance. Even at GM.

Your mention of dampened and/or non-linear gauges is just plain CROOKED ENGINEERING. I am just outright shocked that you said that. It's a cover-up. If you don't want the public to see what's happening then it should be an idiot light. Temp and oil and volt gauges are just that...gauges. They show the variations and people pay extra to see those instead of the idiot light. They WANT to know what's going on. The only thing you would ever wanna damp is the fuel gage...and for obvious reasons. I have a feeling already that some of the temp gauges in these cars have been mocked up to be non-linear.

Until there is some new law of physics that's discovered where fluids aren't used to remove the by-product of combustion(heat), coolant is circulated within an engine block until the desired running temperature is reached, then the coolant is released(and regulated) by the thermostat to be sent thru the radiator. That's how it IS now and Has been over the years on 99.9% of the vehicles out there. By you stating that the stat being located to release HOT coolant at it's rating like this is inferior, then the billions of cars and car manufacturers who design cars would have migrated to your/this setup of the stat being mounted in the cooled return inlet to the block instead. Are All(or even most) of GMs vehicles now cool side stats???...No.... So I don't see where you are coming from saying cooled side Is the "norm". THE HOT side IS THE NORM. SO YOU ARE FLAT OUT WRONG! It doesn't take a "Hot Rodder" to see which way would work better too.

I don't doubt you one bit that TONS of money and work and man-hours went into making a thermostat work on the cold side. I would expect it to. But I Do have to laugh at your off-the-top-of your head figures you threw at me in an earlier post about the water pump flow numbers. YES, I'm Sure the water pump flows that amount. It NEEDS to. And I'm not at All impressed that the water pump can pump on a 6500 rpm motor versus a 5500 motor. That's the operating range of the motor so IT HAS TO. Again, my references are to the stat. Not the pump.

I have to say that I am taking an irritation to this subject and will need to end input to this post because I can see personal pride is getting in the way of open discussion and possible improvement. I was unaware going into this post that you had a hand in the devopment of this cooling system. So I can't fault you for standing behind your product citing millions of dollars and lots of research. GM and other large companies put millions of dollars into research into ALL kinds of things. That doesn't mean they are Never wrong or that there isn't or won't be a better way to do something. I could site examples but that would be sheer offensive and that is not of my intentions at All. If this was the ideal way then it wouldn't have changed at all in new models. Period.

I can also see now why the fan turn-on temps are so high....because too cold of a radiator return temp would cause excessive thermostat closing/cycling. And there you have it... 40 degrees of Swing. The system WILL run better with the AC going too because the fans will always be on(and the condenser will add a little pre heat to the radiator too). I can see why the compressor is on so much now too.

I personally see no way to improve on this setup the way it is other than moving the stat over to the proper side. So you are right in that there is NO room for modification in this configuration. This backwards way is working as well as it possibly could.

None of this is magic or something people would have a really hard time understanding. At times you make people that ask questions feel like they could Never comprehend the setup of the N* cooling system. Yes, there is some initial head-scratching to those used to the conventional cooling system technology. And it Does take a little bit of looking to see how you/they heat up a thermostat that has cold/cooler coolant flowing thru it. But all cooling systems have their basic components and they all no matter how they're mounted all strive to do what they need to do...remove the heat and keep a stable running temperature. When people
want to get into the "meat" of things you at times just throw miniscule engineering "stats" at them just to get them to stop in their tracks. I'm surprised you didn't throw the internal block coolant surface area at me to be honest too. When I mention 40 degree block temps swings you tangent off into flow numbers and hot-spots within the engine. Hot spots and internal temp stabilty are things that engineers fight with to get coolant in between the valve stems and alongside the intake ports and combustion chamber etc.... And they are fighting against the space constraints of the fasteners and the ports, and the plugs...etc...etc... If you wanna talk about hot spots and design, why don't you talk about the inherent properties of All engines where the first cylinder that sees the coolant is the coolest and the one at the end of the line is the hottest, is usually the first to detonate, show signs of wear and/or fail. A couple of degree temp changes in spots within a cylinder head is NOTHING compared to everything "globally" moving up and down 40 degrees. These cars do have inherent early head gasket failures. So far you have not given a reason why personally or from a hands on research standpoint for a cause other that they just wear out like a timing belt. If you are that into this motor than I would kind of expect to see some extended research and data into this subject. But I see you say Nothing of cause or effect other than to discount dexcool as the problem. So I still feel like you're sidestepping getting into the meat of things.

I don't doubt at all that you have run these motors for periods of time without coolant. Like I said, I am not impressed that this motor can run regulated by the computer without coolant in it. If that helped sell more cars, then the added software in the computer was worth it. All it does is get you closer to the tow truck. But like i said, I will BET you one on one that that motor will have a head gasket/oil consumption problem in the not too distant future after that. The expansion rates
of aluminum, steel and gasket materials are all the same no matter whose assembly line it rolls off of.

Something else that you misunderstood what I said....
I said I am NOT changing the stock thermostat! The stock thermostat is 180 FYI. I'd think you would know that. It's in the factory parts book and it's even stamped in the housing of the stat(I'm looking at one right now). And as I said this engine Does not and Will not ever run at that temp because of this stat & fan design. I'm NOT gonna make it worse by trying to go lower! I'm looking to get AWAY from temp swings. You're Not reading what I wrote.

AS I said, I don't see you agreeing with any suggestions for improvement on account of pride. So i'll leave you to rubber stamp the Bars Leak in the lower hose and the timesert procedure.

I think you can tell by now that I am not a mechanic standing around with a flashlight.

It's very obvious that card-blanche was used in the N* development. Aluminum Four valve per cylinder V8's with gyrotor oil pumps, etc are hi-tech, efficient, Expensive and just plain bad-ass. So you can see that GM was passing out alot of money in development at the time. I just think that they/you went overboard on the cooling system and tried to come up with something new and exciting. Just what it see.

I think it's great that you are on here countless hours helping people and giving them
invaluable tips on repairs, shortcuts and just plain being nice. You are obviously a very
nice person. I don't wanna ruin that for others by making you mad. So I am gonna keep my further opinions of the cooling system to myself. You are by far more of an asset to this board that I am. Don't get me wrong, I think the Nothstar engine in itself is something to be proud of. I LOVE it, I love the Eldo body style and I'm gonna be looking into making it's running temp more stable. It's just sad that pride is getting in the way of things now. But I do understand.

It was nice talking to you.

BeelzeBob
02-24-05, 03:27 PM
bluemoon....in case you are still listening....

Nothing personal here at all. Just trying to pass along the facts of what went on in developing the engine and cooling system so that you can understand what works and what doesn't and why.

The issue with an exit side stat is that the stat sees the "hot" water at the thermostat neck. So it opens....and "cold" water from the radiator enters the engine at the far end of the system. Most all systems operate such that the water pump picks up the cold water at the inlet of the pump, pushes it thru the block and then up into the heads. From the heads the coolant is collected and routed to the thermostat. Once the stat sees the hot water and it opens it will flow the hot coolant out of the system until the slug of cold water flushes thru....then the stat starts to close....until that slug of cold water becomes hot water and then the stat opens and the cycle starts all over again. This happens. Worked on cooling systems too many years and seen it too many times on too many different engines. To prevent this, there is always some coolant bypassed back to the water pump inlet to create a positive flow past the stat even when it is closed so as to minimize the thermostat cycling. Look at the coolant bypass circuit on the transverse 4.1/4.5/4.9 pushrod Cadillac engines...that is specifically what it is designed for. All other cooling systems that use exit side stats have some sort of bypass or thermostat bleed to prevent this cycling. Many stats have a simple hole in the paddle to allow a "bleed" of coolant flow to keep some flow past the stat even when it is closed. This obviously hurts warmup performance. When you have a clean sheet of paper and can design the cooling system with the stat where you want it is much easier to put it on the cold/inlet side, design in a coolant bypass circuit that flows over the stat thermostatic element and control the flow of water to the rad that way. In that fashion there is no need to sacrifice cooling system performance or warmup rates by dumming in a bleed or "leak" in the system , nor do any extra external plumbing, to achieve no stat cycling and maximum warmup rates and maximum cooling system performance.

In actuallity, there are several different GM engines and vehicles with inlet side stats.....yes. There have been for years.

Part of the issue is the idea of "right" and "wrong" and the concept that one way must be THE right way. Both ways work. An exit side stat can work fine and an inlet side stat can work fine. There are advantages and disadvantages to both. Most "pros" end up on the side of the inlet side stat...but it requires an engine cooling system and water pump and pressurized surge tank to work correctly so it will not show up on engines until they are redesigned to incorporate the system fully. An inlet side stat does allow superior thermostat cycling performance and provides this control with no loss of warmup performance due to unnecessary bleeds or bypasses of the stat. I never insinuated that the cold side stat was "the norm"...just that it can provide superior cooling system performance..if it is designed correctly. I am NOT wrong on that fact. I understand that most cars "that you are likely familiar with" have exit side stats....I have a couple of old muscle cars, too. But the inlet side stats work better. I doubt that most of the "hot rodders" are ever going to understand this as they do not generally understand what a cooling system has to do or how it really works...LOL.

Most "hot rodders" still think you have to slow the coolant down so that "it has time to pick up the heat and time to release it in the radiator."...LOL LOL This is so far from the truth that it is rediculous but it is still repeated to this day in hot rod magazines of all type. So...I would expect a "hot rodder" to think an exit side stat is better "because that is the way it has always been".....duh...


The radiator that rejects the heat does not care where the stat is at.....it just sees the flow. The coolant circuit to the rad can be controlled on the inlet to the rad circuit (a hot/engine exit side stat) or on the exit of the rad (the cold/water pump inlet side stat). It makes absolutely no difference to the rad. The flow is the same. Kind of like interrupting the circuit for the light bulb.....take away the volts or the ground and the bulb goes dim.

If you are not impressed with the 105 GPM flow rate of the Northstar water pump at 6500 then it is obvious that you know little or nothing about cooling systems in cars. That is a major major amount of flow increase compared to systems prior to 1993. It definitely broke new ground for flow rates, water pump design, etc... for engine cooling system. I actually did some of the early work in the mid 80's regarding establishing the bogey flow rates required to thermally stabilize an engine making that level of power. We did developement work using two and three water pumps cobbled onto an engine to get sufficient flow. The pumps and engines you gained experience with that are made prior to 1993 pump WAY WAY less coolant. Way less. It took a lot of time and development to get a water pump on an engine that would flow that level of coolant. The old pumps will just not do it. Speed them up and they cavitate and stop pumping. This is also what led to the pressurized surge tank to pressurize the water pump inlet to prevent cavitation.

I personally knew John Lingenfelter before he passed away. GM has worked closely with him on may projects...all high performance related BTW...nothing production related. I personally helped him with the valve train on the Ecotec motor that they were running in the drag race series for sport compact cars....the one running 40 PSI turbo boost that was blowing the intake valves open...LOL. I know exactly what kind of cars and engines he builds. They make some high performance stuff....but.....not the kind of stuff to run hundreds of hours of dyno endurance without breaking and the power numbers that they come up with are indeed flash dyno readings on a quick pull or a transient pull on an inertia chassis dyno. Lingenfelter's organisation does excellent work (my neighbor finished the One Lap with a Lingenfelter CTS-V and owns the supercharged CTS-V that was in the Car and Driver shoot out several months ago...) but they build race cars...not stuff to haul butts for hundreds of thousands of miles. Sorry to burst your bubble.

Crooked or not....that's the way gauges are set up.....LOL. Even some of the very expensive aftermarket gauges are heavily damped. I have a Autometer mechanical coolant temp gauge on my garden tractor that I installed (an engineer never trusts the engineers that designed the device so I can relate to your feelings.....seriously). I also installed a quickie, instant response K type thermocouple for a temporary check of the gauge calibration. That Autometer gauge has enough damping in it so that it does not respond to the 8 degree F thermostat cycling that I see with the thermocouple!!! So.....the things you take as gospel may not be.....be aware.

If you really want to be livid over passenger car OEM gauges I will tell you that there is more than one application where the oil pressure guage is really a dummy reading. Purely for show. It is fed a signal/data generated by the PCM based on oil pressure, coolant temp, etc. The engines do not even have an oil pressure sending unit on them...!!!!! Purely fictious readout. LOL LOL True. It looks and responds exactly like the engine oil pressure should...but it is just a generated signal. PS...there is an idiot light also....

The AC compressor run time has nothing to do with keeping the fans operating....duh....think about it. If that was the simple goal then why didn't we just make the control system run the fans regardless of whether the AC compressor was possible or not??? It would have been much easier to do this than run the compressor too much as you imply.


BTW....your personal pride is getting in the way of future conversation...not mine.....LOL.... I try to provide as much fact as I can and insight into how the systems were designed so that people can understand what all is involved. If someone cannot grasp what the significance of a fact or figure that I provide is about then it is not because I am trying to snow them....maybe they really don't understand exactly how the system works....

blunted
02-24-05, 10:28 PM
Well I must say I have learned a nice amount from this thread, thanks in part to Blue being so stuck on his preconcieved notions that Bbob went and explained this interesting system with great detail. Blue, I wouldn't take the way things are said personally, they are just direct and to the point answers which is what you should expect from a cadillac engineer! If your detecting some sort of tone in the statement maybe its from him having to constantly re-iterate things to everyone and being challenged by people who think they know these vehicles better than the person who helped create them. Bbob is always helping everyone on the forum and for that I must say Thank You! If it wasn't for this forum I wouldn't know my head from my ass when it comes to my Eldorado. :shhh:

dkozloski
02-25-05, 01:20 AM
Bbob, is there a peer reviewed paper available on the North* cooling system? It seems very simple to me; much like the blended flow systems used to regulate the temperature of a radiant floor heat slab.

LCLCLC
02-25-05, 04:05 AM
Kind of a minor point to inject into this discussion....

I was really impressed with the oil pressure that my 94 Ranger 4L kept. It went right up to about 3/4 gauge. And stayed there. And after running on a hot day and going to idle, by golly, it still kept 3/4 gauge. I thought, hummmmm, this didn't seem quite right to me. But maybe those Ford engineers have a high volume/pressure oil pump, with internal bypass valves so it will always keep a nice high pressure.

Then I started reading on the internet. What do you know, this gauge is really just an attractive idiot light. The oil pressure sensor is an on/off switch calibrated to about 5psi. Anything below, no gauge, anything above gives 3/4 gauge. I don't know exactly what year they started this, but it continues in the new models also.

I felt kind of like the singer of the song 'Angel In A Centerfold', when he sees the centerfold picture of the girl he always idolized in school.....

I wonder how many other Ford and other models' oil gauges are also on/off switch displays????

But, still, "I Love My Truck". Just another small eye-opener about how the world actually works.

dkozloski
02-25-05, 12:02 PM
LCLCLC,My '95 Ford Ranger has three positions to the oil pressure gague; on the pin, barely off the pin, and about 1/2. While driving, it switches between barely off the pin to 1/2 for no apparent reason. This must be a product improvement meant to simulate real life.

STS 310
02-25-05, 03:10 PM
This was a great thread. Very informative AND entertaining. Thanks!

Ranger
02-25-05, 11:01 PM
I have to admit, I feel a bit decieved by these "dummy" guages. I'd much prefer a "real" guage and if that causes a problem then the manufacturer should put a good explination (like Bbob would) in the owners manual. Same goes for the oil consumption. It would not be concived as a problem if it were explained to people. If people are too stupid to read it then so be it. Explain it to them when they make an unnecessary trip to the dealer.

blb
02-27-05, 01:39 PM
Pretty good rant but I think you're just a litle bit late. My '04 CTS with the VVT V6 North* has an analog temp gauge that never budges off the straight-up mid range mark from ambient of -49F to +95F over any terrain. What ever the problem may have been, has been designed out of the newer motors.

dkoz....the truth is, your analog temp gage has been turned into nothing more than an anolog idiot light by the GM engineers you speak of so highly. The thermal swings are still there in your '04 CTS, it's just that your gage has been "dummed down" so that the customer no longer sees the routine temp swings, and the dealers and GM no longer have to deal with the customer complaints. GM has been doing this with temp gages on many product lines as far back as model year 2000 and quite possibly a year or two earlier on some vehicles.

If you want to keep fooling yourself that "whatever the problem may have been, has been designed out of newer motors" as you say, go ahead and believe it if you want to. Since you seem to think very highly of bbob, ask him to confirm the temp gage information above, specifically on your '04 CTS .

dkozloski
02-28-05, 01:44 PM
What does it matter as long as the gauge gives all the information that is required to operate the vehicle safely? To paraphrase Shakespeare, "The temperature swings are a lot of sound and fury, signifying nothing". Who is more qualified to pass judgement on the importance of the temperature fluctuations? An armchair quarterback who sits back in his Lazy-Boy, looks at the ceiling and says ,"I think there is a problem with the temp swings", or the engineering team that spends thousands of hours in the dyno room and hundreds of thousands of miles on the test track and comes back, "You don't know what the hell you're talking about. Here is the real data compiled and collated".

Stoneage_Caddy
02-28-05, 03:10 PM
dkoz....the truth is, your analog temp gage has been turned into nothing more than an anolog idiot light by the GM engineers you speak of so highly. The thermal swings are still there in your '04 CTS, it's just that your gage has been "dummed down" so that the customer no longer sees the routine temp swings, and the dealers and GM no longer have to deal with the customer complaints. GM has been doing this with temp gages on many product lines as far back as model year 2000 and quite possibly a year or two earlier on some vehicles.

If you want to keep fooling yourself that "whatever the problem may have been, has been designed out of newer motors" as you say, go ahead and believe it if you want to. Since you seem to think very highly of bbob, ask him to confirm the temp gage information above, specifically on your '04 CTS .

too bad they didnt do this on our 2004 Malibu Maxx ...the car acutally gave us a inicated overheat (in the red)..I had to shut to car down as it "cooked up" so fast and i was afrid to run it....GM looked at it and said the "event" was normal....They replicated the "event" for me ...i then asked "ok i see that the fans kick on too late , why doesnt the ECM anticipate this "event" and kick the fans on early to attempt to keep it stabilized"....As usual the "know it all" sevice tech shrugs his shoulders .....

Not doubting , im sure there a good reason for it all ....but GM just bought back our MAXX (other issues too) so im wondering ....

dkozloski
02-28-05, 03:31 PM
Back in the days before all this precision computer control we used to think that the cooling system was doing okay unless Prestone was coming out the overflow onto the road. Next came the catch can to feed the overflow back to the system. Now we have surge tanks, electronic fans, and the Lord knows what else, but it appears to me that the old rules still hold; if it's not spitting coolant out the vent everything is okay. You can't design a system to account for every transient one-in-a-million event. It seems to me that I read somewhere that the design criteria for an American car is for the cooling system to allow you to operate at 100MPH on a 100deg F day with a 100MPH following wind. It sounds good to me.

Stoneage_Caddy
02-28-05, 03:36 PM
thats what i figured ...but some technicains paint apicture that the modern engine is very fragile ....so i err on the side of caution and shutdown when the temp gauge does a acrobatic performance on my instrament cluster...not something im used to seeing ....

blb
02-28-05, 06:47 PM
The point is, the temp gages are now so desensitized, that you no longer have the aibility to see a trend and react in time to do something about it. It's just like an idiot light now. The gage will stay in the center until you reach the point where the vehicle is overheated and then after it's too late, the gage will show an overheat condition. Sounds like a typical GM cost cutting solution.

GM focus group: So we have many customers complaining that when they sit in Arizona-like summertime traffic jambs, their coolant temperatures keep rising and rising steadily over the period of an hour, clear past 245F which appears as though a thermal runaway situation is occuring. This causes them concern.

GM Management: Stupid customers. Engineering says there's nothing wrong with this situation and this heat is good for the engine and won't cause head gasket failures. Besides, redesigning the cooling system to prevent this will cost millions and the revenue lost at the dealerships replacing headgaskets and timeserts will also be huge. In order to protect shareholder value, lets desensitize the gage so the stupid customer doesn't realize that his engine temperature is so high.

Focus group: Protecting shareholder value....Sounds good to us!

.....and the loss of GM market share continues while the imports gain......darn shame!

cadillacmike68
03-01-05, 01:25 PM
Now that was some serious reading!

I have a 2000 Eldorado ESC, my 5th Cadillac but my 1st NorthStar. I got in Aug, but my wife had it until dec. So, this one is newer than a 94 but older than the new 04s. BTW my 1995 Fleetwood RWD has 2 electric cooling fans also, and NO temp gauge :helpless:

Bluemoon, how did you get a digital readout on your coolant temp???? I have an analog gauge that I now know to be working just fine as I will detail below, but it doesn't have any numbers on the dial.

My Eldorado's gauge pretty much would climb up to the midway point within 3 minutes (I would watch it to ensure it wasn't "jumping" up as in a faked out idiot light). Then it would sit there. FWIW, My old 1968 DeVille Convertible takes 8-10 minutes to go to normal range.

Last week, in heavy traffic and a slightly warmer day, I noticed it wandering around the hot side, one quadrant over to the right. Needless to say I was a bit concerned. But it never went past the next hash mark, and then as the traffic cleared, it went back down to 1/2. That evening, same thing, fine until I got into heavy traffic, creep up 1 hash mark, go back down to 1/2 after traffic clears. When I got to my meeting (Cadillac Club monthly meeting) I sat in the car for 15 min trying to get it to heat up again. I noticed only 1 of the 2 fans was running (climate control fan), but since the temp gauge wasn't creeping I couldn't tell if the other fan was bad or not. The outside temp dropped too, making it impossible to make any further determination.

So I got to thinking. This past summer, my Fleetwood demanded an oil change less than 1000 miles after just changing it. I was like WTF, but had it changed again. I checked the fans, remembering that way back when I had a Fiero (oh yeah, couldn't afford an Allante) when its SINGLE electric fan went bad, the temp gauge would creep all the way up in stopped traffic.

So I checked out the Fleetwood's fans. the PRIMARY fan wasn't spinning. Funny, no temp warning on the idiot light tho'. So I bought a new motor, and changed it out (easy on a Fleetwood). Primary fan runs, several thousand miles and the car isn't complaining about an oil change yet. What must have happened is the alternate fan must khave been trying to take up the slack, but it's smaller than the primary fan in the Fleetwood, and probably wasn't enough to keep things as cool as the car wanted, but apparently not bad enough to cause an overheat :suspect:

But, the engine oil life monitor (primitive in the 1995 Fleetwood, no % remaining indicator, just a "change engine oil" light that comes on) noticed the increased temp and decided it needed new oil.
So now I'm a firm believer in that system as well :worship:

Back to the Eldorado. I brought it to the dealer (they had a brake special I needed brakes, and I have the money to pay their outrageous charges). Guess what they found? The primary fan was disconnected :confused: How did that happen? I didn't touch it (they NEVER had it), maybe that ice storm in Atlanta messed it up, beats me but they re-connect it and the fan operates. And no more dancing gauge.

So why the rant - I think the gauges work fine (unless it's FUBARed) they are not overly "damped" at least not in 2000. and they can actually help you spot a minor problem before it gets to be a major problem.

Here's another thought,, I ALWAYS run the Fleetwood with the Climate Control on Auto, why do you think I buy Cadillacs, maybe 1 month per year in FL, I can put it on "econ", but that's it. That probably masked the Fleetwoods problem, (that and the NO TEMP BAUGE BS:disappoin ) Where the Eldorado, being a convertible is a different item, either top up and Climate Control on Auto or top down fan on and "AC OFF" mode. That tends to keep the secondary (or AC fan) running which will temporarily mask a primary cooling fam problem unless you're stuck in traffic for like an hour.

So there you have it, I'm a believer in these engine systems now. Maybe in the future I'll have to get a new RWD V8 STS :D

Jack Ammann
03-03-05, 05:43 PM
***My background is NOT a Hot Rod magazine reader. That I found to be an outright insult. Especially since you don't know who I am or where I'm coming from.***

Mr Bluemoon, That's absolutely correct. So why don't you tell us "who you are" and "where you're coming from". That'll certainly give you some standing. Afterall we know who Bill Bobynski is and where he's coming from.

BlueMoon
03-04-05, 05:06 AM
I'm not looking for any "standing" whatsoever on here. I was looking to spark some discussion into improvement of the longevity of these motors. And I noticed from searching the forum that people who bring up changing their cooling system's operating characteristics are just time and time again shot down by being told "That's the way it is...Leave it alone...You're looking to fix something that ain't broke...,etc...". So I can see now that I'm not gonna get anywhere by making or sharing any suggestions. I have my opinions as I have already expressed about running temps and swings. And I mentioned them initially not knowing bbobs involvement. So I apologize for coming on here with Guns-A-Blazin.

I also have to be Very careful here with my issues & points because as I stated, bbob is an asset to this board. Although I disagree on a few things with him, I don't wanna "look a gift horse in the mouth" and possibly ruin things for others. I did lose my "cool"(pun intended) and walked away just to keep from lashing back because of a couple of things and how they were handled tho. One of them was the even SUGGESTION of damping out 40 degrees of temperature swing from the consumer. That flat out PMO.

People who want gauges like to pay attention to the way their engines behave and for good reason. They get to know the normal needle movements for their car under different conditions and they watch them to catch problems BEFORE they become bigger, more expensive ones(like before they spin bearings and damage cranks, and blow all the coolant out on the road and possibly blow their head gaskets and/or cause other more severe damage). They WANT and pay extra for that. Sure, there's always that one old lady out of millions of customers who comes in with a seemingly dumb question. But that/she's normal and Not an excuse to hide things and/or save money. Think of it this way... if a car company saves ONE DOLLAR per vehicle by putting just a temp SWITCH in(or nothing at all) instead of a variable resistor for a sending unit in ten million cars, somebody(an engineer or a CEO) is gonna walk away with a Nice Fat Bonus...say Ten Million Bucks($1 x 10,000,000=$10,000,000). Sure, most people might not Ever notice, but the fact of the matter is, it's SAD. (And borderline deception). Especially in Cadillac. This is SUPPOSED to be GM's(and in my opinion America's) top-of-the-line. If I'm paying for a TOL car with gauges... I WANT A
GAUGE THAT'S LINEAR AND RELATIVELY ACCURATE! If it's not really a gauge, THEN PUT A LIGHT IN IT!

Also, the "Duhs" and "Lol's" were more of an irritation than anything else. They get in the way of some good back-and-forth technical dialog. And for those who ask seemingly dumb questions looking to learn something, it's kind of demeaning.
Otherwise, I'd Love to have some more in-depth discussions of the N* cooling system. Only good can come out of it. Everyone benefits.

As you can tell I'm not a "fan" of high running temps and big temp swings are a big red flag in my book. But as I said, all of what I share is opinion. I don't expect everyone(or anyone) to agree with me.

So think of me as just another average-Joe car buyer. Really that's all I am.

For those of you whose toes I stepped on and want to know who I really am, I'm truly sorry. My name is Brian and I'm from Chicago. I don't have any impressive credentials to share with you(like wrenchin' with Smokey Unik or havin coffee with Al Capone). All I have to offer is a couple of thoughts and some keystrokes.

Go GM... Go Caddy.... Buy American.
Let's stay on top.

BeelzeBob
03-04-05, 01:02 PM
Bluemoon....having read back over this thread I think that we are on more common ground than you realize....

I agree with you totally in theory that the coolant temp changes are detrimental, to some extent, to the life of the engine. Anytime the engine changes temperature the aluminum and steel parts change size due to expansion and contraction and , as a result, load the gaskets and such. It is all lumped under the context of "thermal fatigue". The engine would certainly last longer (whatever that means....LOL) if it never changed temperature and always ran at the exact same temperature. But it cannot. People must and will cold start engines and shut them down for the night and such.....so.....that is where the items that I tried to elaborate on come into play.

There is far more thermal fatigue induced by coldstarting and warming up the engine compared to allowing the coolant temp to drift between 190 and 225. That is why I tend to down play the coolant temp swings that you dwelled on as they are minor compared to the major effect of thermocyling the engine from -40 to 225 and back to -40 (people do live and drive to work in Kapuskasing and Fairbanks and do this regularily in the winter)

When the engine was designed it was understood that the all aluminum engine would be very sensitive to thermal fatigue (aluminum expands more and works the gasketed joints much more) and great pains were taken to minimize the effect of it. The Northstar cooling system is designed to mitigate the effects of the thermal fatigue issues by flushing the coolant thru the engine and bypass loop at a very high rate. This allows the whole engine and all the parts to change temperature at the same rate thus preventing huge thermal gradients within the engine that can do far more damage to the gaskets and seals than simple changes in coolant temperature. No BS here and not trying to snow under your concerns....just trying to make the point that they were understood and addressed and have been taken into account.

An older engine with an exit stat might appear to run at a more fixed temperature....but there is really no reason for it to do that. If the exit stat sees only the exit/hot coolant then it will open and allow cold water into the engine from the other end. Then the cold water will flush thru the engine until the stat sees it and closes. There are usually fairly wide temperature gradients within the engine and some fairly large coolant temperature swings with those systems...you just may not have seen them due to the gauge in question at the time.

The inlet stat, combined with the very high coolant flow rates and very high internal recirc rates keep the engine internally at a constant temp and , when the coolant temp does change (due to fans off idling...for example) it allows the entire engine to change temp evenly thus mitigating the effect of the change.

Take a look at current engines and you will see inlet side stats, high flow water pumps, high internal recirc rate passages, etc. The Northstar engine pioneered this approach and it works very well. I am not saying to "just leave it alone"....I am saying to understand how the system works and why it does certain things before you start trying to improve it. If you do understand it and see the flow work and developement put into the system I suspect that you would have far more confidence in it and would be more reticent to advocate changing it or describing it as a poor design.

My point about the guages was meant to point out that you may have been mislead in some of your earlier observations about the thermal stability of the cooling systems on the older cars. Not just GM gauges are damped but ALL guages are damped to some extent and can cover up many small changes in temperature and pressure. Want to see each pulse of the oil pump gerotor segment for example....??....run a 3/8 line to the gauge and pull the orifice out of the gauge inlet (just about every mechanical oil pressure gauge has one to damp the needle movements) and watch the oil pressure. You will learn that "oil pressure" that you are used to seeing with a 1/8 line and a restrictor in the gauge is not really what is happening. Same with mechanical coolant temp gauges. You might be surprised at what you see.

The vast majority of people driving the vehicles have NO IDEA about what the gauges are telling them so there is really no point in them. Idiot lights are fine for the vast majority of the population. Myself included. I would notice an idiot warning light while driving but rarely watch the guages closely enough in day-in/day-out driving to spot a catostrophic, sudden failure. So the guages that are provided are designed to not provide TOO MUCH information so as to create unnecessary panic and concern with the owner. Simple as that. It is far easier and more effective to do this than to educate every owner on exactly how the guage is calibrated and how to interprete it, etc...

Finally, any vehicle with electric cooling fans is going to exhibit some coolant temperature swings when idling, cllimbing grades, etc. Large, high capacity, engine driven fans are great for moving large amounts of air and are a necessity in trucks and such for moving heavy loads and trailer towing. In a passenger car they are not necessary, are very noisy and hurt fuel economy tremendously....so....electric fans are used and their operation is minimized for NVH reduction, electrical load reduction, etc. As a result, with no air flow (AC off or in econ or in cold weather with AC defeated) the coolant temp swings slightly. This is nothing to be alarmed about for the reasons mentioned above. The system is designed to protect the engine against FAR GREATER coolant temp excursions than what you describe so the slight swings due to idling and such are really very minor.

Benlomand
03-04-05, 07:03 PM
Heavy Rap dudes!

blb
03-05-05, 11:08 AM
There is far more thermal fatigue induced by coldstarting and warming up the engine compared to allowing the coolant temp to drift between 190 and 225.


I don't think anyone will disagree with the statement above. And if the coolant temps in these engines only drifted between 190 and 225F, there wouldn't be anything to discuss. I don't think anyone would consider this out of the ordinary. You are downplaying the thermal swings that have owners concerned.

It's when you sit in a traffic jamb in the middle of summer in 100F ambient temps, and the coolant temps rise slowly, but steadily, over the course of 45 minutes to an hour, to 240F and past, and never seem to level off, that gives the perception of thermal runaway due to an inadequate cooling system.

BeelzeBob
03-07-05, 12:21 AM
I don't think anyone will disagree with the statement above. And if the coolant temps in these engines only drifted between 190 and 225F, there wouldn't be anything to discuss. I don't think anyone would consider this out of the ordinary. You are downplaying the thermal swings that have owners concerned.

It's when you sit in a traffic jamb in the middle of summer in 100F ambient temps, and the coolant temps rise slowly, but steadily, over the course of 45 minutes to an hour, to 240F and past, and never seem to level off, that gives the perception of thermal runaway due to an inadequate cooling system.


If you read thru the earlier posts you will see that the discussion revolved around the coolant temp cycleing between the stat temps and the fan on temps.......

I understand what you are saying but it really is pretty rare for the coolant to get up to 240 and above. Cars in city traffic in very hot climates will see those temps on occasion but that temp is well within the operating range of the cooling system and is not considered "hot" at all. It might be perceived as a "runaway" condition or a sign of "an inadequate cooling system" but it really isn't. Just one more instance of how people do not understand how the cooling system works and what the coolant temp gauge is really telling them. IT is far easier to just eliminate the gauge than educate them all....really. That is what the idiot lights are for...to tell you when you are having a problem. if there are no warning lights then QUIT WORRYING.

The Northstar cooling system has several levels of warnings to alert the owner of a potential problem. First the real time coolant level alarm would indicate low coolant. That is part of the purpose of the pressurized surge tank...to provide a high and quiet place in the cooling system to allow a real time low coolant alarm before any damage can be done to the engine. Secondly, if the coolant does get too hot the AC will be shut off to aid in cooling the radiator and reduce load on the system. Third, if the coolant temp continues to rise the warning lights and messages and chimes make it unmistakeable that the engine is overheating. Fourth, if the engine gets really really hot then it will automatically revert to the loss of coolant limp home mode (the "camel mode") to enable the car to be driven to a safe place to determine the problem. Fifth, the coolant temp sensor is strategically located in a specially designed and located boss in the cylinder head itself so as to detect coolant temp as long as the system has coolant in it and to instantly detect the hot metal temperature of the exhaust port wall if the coolant level drops enough to make the heads dry. This is important as some engines have the coolant temp sensor in the intake manifold and are "blind" to an overheat of the coolant is very low or is lost suddenly as the sensor will not be seeing the hot coolant once it drains down below the level of the intake.

With all the coolant temp controls and protection on the engine watching the coolant temp gauge and trying to second guess what is going on is crazy. Put tape over it and relax.

blb
03-07-05, 01:21 PM
If you read thru the earlier posts you will see that the discussion revolved around the coolant temp cycleing between the stat temps and the fan on temps.......

I understand what you are saying but it really is pretty rare for the coolant to get up to 240 and above. Cars in city traffic in very hot climates will see those temps on occasion but that temp is well within the operating range of the cooling system and is not considered "hot" at all. It might be perceived as a "runaway" condition or a sign of "an inadequate cooling system" but it really isn't.

If the coolant temperature steadily and continuously keeps rising past 240F, at idle in 90F to 100F ambient temps, and both cooling fans are running at maximum RPM, that tells me that the thermodynamic system is creating more heat than can be disipated due to the constrtaints of the cooling system.

Cycling between the stat temps and fan on temps has nothing to do with anything in this example since the 240F coolant temp is way past both the stat temp and fan on temps.

Knowing that the system is designed to take evasive action (shutting down the A/C compressor to eliminate the thermal load of the A/C evaporator) somewhere after 246F and shutting down the fuel to the cylinders is something that should not be part of normal everyday operating parameters.

The vehicle that I routinely experienced 240F+ coolant temps in city traffic in 95F ambient temps after an hour in the summer was a '94 STS. Have the later models had changes in the cooling fan design, cooling fan RPM capability or changes to the fan on temps to prevent this non-stop Temp rise?

cadillacmike68
03-07-05, 01:37 PM
"One of them was the even SUGGESTION of damping out 40 degrees of temperature swing from the consumer. That flat out PMO."

As I stated earlier, I don't think my temp gauge (2000) Eldorado (and any prior years) is damped. I noticed a slight movement again esterday, driving home from Orlando to Tampa, top down, climate control OFF (secondary cooling fan off as well) and the gauge moved slightly to the right as I was stuck on I-4 with warm temps outside. I turned on the climate control (secondary fan comes on) and it cooled off the system (and me as well :) ), gauge moved back to the left to it's "normal" position.

We're talking less than 1/2 a hash mark here, hardly expected of a "damped" gauge.

BeelzeBob
03-07-05, 02:14 PM
If the coolant temperature steadily and continuously keeps rising past 240F, at idle in 90F to 100F ambient temps, and both cooling fans are running at maximum RPM, that tells me that the thermodynamic system is creating more heat than can be disipated due to the constrtaints of the cooling system.

Cycling between the stat temps and fan on temps has nothing to do with anything in this example since the 240F coolant temp is way past both the stat temp and fan on temps.

Knowing that the system is designed to take evasive action (shutting down the A/C compressor to eliminate the thermal load of the A/C evaporator) somewhere after 246F and shutting down the fuel to the cylinders is something that should not be part of normal everyday operating parameters.

The vehicle that I routinely experienced 240F+ coolant temps in city traffic in 95F ambient temps after an hour in the summer was a '94 STS. Have the later models had changes in the cooling fan design, cooling fan RPM capability or changes to the fan on temps to prevent this non-stop Temp rise?


The evasive action of turning off the AC happens at about 258 degrees coolant...way beyond the range of any normal operation. The loss of coolant protection and such is action taken to protect the system and engine once it has gone out of control for some reason. I was not mentioning this to imply that it was "normal" or something that would happen in daily operation..only to help people understand that the engine and system is protected against damage if things DO get out of control and they they should realize that the system is operating normally as they are NOT getting into these warnings and that the engine and system will not be damaged if it does go out of control for some reason so they shouldn't worry.

Extended operation in high ambients in city traffic with AC on and such can cause the coolant temp to go to 240 or above....yes....so what??? That is fine and well within the operating parameters of the system. If the system was generating more heat than it could eliminate it would not stop at 240 or 250 or 260....it would boil over continuously. The fact that the temperature slowly creeps up (over the period of an hour in traffic...???) and does not go ballistic, the AC does not shut off, it does not boil, you do not get any warnings, etc....means that it is operating fine. Drive it and forget it.

The cooling system is sized for all cars from Kapuskasing to Phoenix to Saudia Arabia. Actually, very few people in the millions of Cadillacs on the road sit in Pheonix city traffic at over 100 degrees ambient....but.....the system is sized to operate there with no problems. It will run higher coolant temps in those conditions than in cooler ones but it doesn't mean anything is "wrong" per se or that the system is mis-designed or mis-sized. The low fans only kick on 225 and 240 casues high fan operation...so the sytem isn't even operating at max cooling capacity until it gets to 240. That is how it is designed because it works fine like that. Actually, the hotter the radiator coolant is the more efficient the radiator is...i.e..the delta temperature between the coolant and the air coming thru the radiator is greater. So, hotter coolant is GOOD for cooling efficiency and allows lighter weight radiators, less electric fan electrical load, less noise due to fan operation, etc.

gtm2u
03-07-05, 08:46 PM
bluemoon....in case you are still listening....


If I may jump in here with some of my own issues concerning the torn threads which can be found in hundreds of different sites. This suggests it is much worse than Cadillac would ever admit in any public disclosure. I've worked as a professional mechanic and other related skills for decades on aluminum block engines and never seen anything like this.

I don't know where to begin, first the length of the head bolts threaded into an aluminum engine do not meet what are considered industry standards for 2.0- 2.5 X diameter vs length assuming they were even the correct pitch. Using a 4 bolt clamping and the torque values given they barely meet the needs of containing combustion pressures with safety factors. I believe it's common knowledge that studs are far superior because they can be made from better alloys cheaper than a bolt having to have a head formed and the shank formed. Who in their right mind would consider flirting with head bolts that were too short unless they just happened to have a contract for a few million and didn't want to renegoiate for new design which would reflect inflated costs...

Since my torn thread job is still pending and I intend to replace with studs I've not examined the length of the replacement bolts but discussing with other Cadillac mechanics they did not indicate the depth was increased. I have examined the Timeserts and find that though they may have been adequate if the bolt length was increased to utilize the 30mm length it was never done. I've used Keenserts and Slimserts for almost 40 years as a repair for torn thread in aluminum engines. This technology has been used in European engine design when the engine was originally conceived because of it's superior holding ability. These inserts in some cases were part of the casting process and in others were installed after as part of the machining process. I would hazard a guess GM was well aware of what the European high end market was building as far back is the early '60s yet they elected to ignore the engineering behind these improvements. The Aerospace industry has been using these inserts in original design and to repair damaged threads but I've seen no claims that Timeserts meet Mil. Spec. as do the other makers.

If you look at the early days of the Lancia V6 their studs were copper plated to reduce electrolysis from all the metals involved in the cooling system. This included "bonding" those parts to reduce the corrosion from the dissimilar metals. This is the same engine (D50) that they gave to Ferrari complete with all patent rights after 2 of their drivers were killed in one year. This was the engine which GM said couldn't be built and couldn't be balanced yet they waited till the patents ran out and look what we have now.

I can only conclude that engineering staff either didn't know or were ignored because of budget issues assigned to every fastner used and thus were forced by Admin. to use inferior standards and/or materials. The fact that they have at least increased the pitch in 2004-2005 engines suggests that the cost savings has backfied in increased warranty claims which offsets what they saved.

Cheers,
GTM2u

dkozloski
03-07-05, 09:14 PM
Well Bbob, another gauntlet thrown down. I'll hold your coat for you.

blb
03-07-05, 10:33 PM
Well, all I keep hearing is how headbolts pulling out of aluminum blocks and headgasket failures are no big deal and we should learn to live with them. Also, we keep hearing how high engine operating temperatures have nothing to do with it. My personal experience is that after 30 years of driving all different makes and models, only a meticulously maintained Northstar Cadillac with under 50,000 miles has ever stranded me hundreds of miles from home, causing me to have to repair the POS in a hotel parking lot, finishing up at 2:00 AM. I absolutely had to be on the road the next morning at 7:00 AM, so jobbing out the repair was not a possibility. Fortunately, I realized early on, that on any trip, carrying a complete set of tools and a floor jack was absolutely essential with these cars. These are the times that are not easily forgotten and at least part of the reason GM's market share continues to dissolve each and every year. Although the wail and power of the Northstar at WOT is truly a thing of beauty, it is simply not worth having to put up with subpar quality, horrible reliability and deplorable resale. I keep hoping to hear that GM realizes that improvements can be made and there is an ongoing effort to improve the reliability of these cars. But, all I keep hearing is that everything is wonderful as is, and there are no problems. Sadly, this type of arrogance will eventually bring the once great GM to its knees, put many good people out of work, and allow Toyota and other import manufacturers to easily become the biggest auto manufacturers with plants in the US in the near future. What a shame.

BeelzeBob
03-08-05, 12:42 AM
Regarding mr. gtm2u's comments.....

Actually, when the Northstar was designed the head bolt thread engagement was GREATER than the industry standard recommendations for bolts into aluminum. The Northstar head bolts provide more than 2 times engagement and the bolt length has been upgraded over the years to 2.5 engagement. You are asking the wrong sources for your info....check partnumbers instead.

First time I have ever heard anyone accuse the Northstar head bolts of being too short...????.... given the long grip length of the production bolts they have PLENTY of room for elongation as they are tensioned....that is why they are so long and why the threads for the head bolts are down into the bottom of the cylinder bores to tie into the lower structure of the block. In fact, they are some of the longest head bolts in the market place. I can take you to a display of competitive aluminum engines and show anyone interested that the all knowing "Europeans" use even shorter head bolts in aluminum blocks with shorter grip lengths...hmmmm......

The idea that "Using a 4 bolt clamping and the torque values given they barely meet the needs of containing combustion pressures with safety factors." is absolute nonsense. If this were true all Northstars on the road would loose the head gaskets and have trouble sealing compression all the time. This is another one of those claims by a supposed expert that doesn't even pass the common sense test. There has been EXTENSIVE clamp load development done on the Northstar head gasket joint starting years before the engine actually went into production. The head bolt joint is fine. Interesting, that if this claim is even remotely true, that the supercharged Northstar seals nearly twice the combustion loads with the same head bolt arrangement, same tensioning procedure, same length bolts, etc.... True, the thread pitch has been upgraded to the 2.0 mm pitch bolts but the clamp load generated by the torque/angle procedure is the same.


Since the author of the post above refers to the "torque values given..." I suspect he actually knows very little about the joint other than internet reading and possibly talking to others. The bolts are tensioned via a sequence of torque and angle specifications. Since he doesn't mention the torque/angle specs I would question how much he really knows about the joint. The bolts end up being tensioned to more than 40 kilo-newtons of load. Without the individual posting his claims knowing the metalurgy of the bolts, the amount of bolt stretch, etc.... he cannot have any idea of what the clamp load is. The clamp load stated is far far beyond what is required to seal combustion. In fact, the head bolts will actually seal combustion at slightly less than 15 kilo newtons of load per bolt.

I would also be interesting in escorting that individual thru the display of German, Japanese, European and other competitive aluminumn engines and letting him point out the use of "inserts" in the aluminum blocks to me....LOL....I'll spare you the expense...they do not use them either.

Telling me what Lancia did is a joke....LOL....last Lancia I saw was rotting away in my neighbor's garage. It was rotting away faster than he could try to patch it up to "restore" it to sell it. We actually ran several Lancias on our durability tests years ago...it was a short test when the doors literally fell off within 5000 miles. Seriously.

BTW....plating the head bolts if they are exposed to coolant might be required but even the most elimentary examination of the Northstar block or photos in the service manual or on this website you can see that ALL the head bolts are in their own, dry, sealed cavity with no coolant or outside contaminant intrusion. Another small detail overlooked in this analysis.

Studs....sure. you can make studs out of anything and, yes, it is cheaper and easier. But, try making 1200 engines a day with studs. Impossible to do and impossible to assemble. With Ferrrari volumes or such....maybe. Not a high volume production engine. You cannot easily line up the head to install it on all the studs simultaneously and you cannot protect the head deck surface from damage from all those studs trying to line it up. Get real. Only someone who has never assembled something like that would come up with that idea. The Northstar head bolts are not the "cheaper and easier" approach. The bolts are a high strength, specialty alloy. Yes, it cost more to head and form the threads and such. So, we are faulted for doing it the more expensive way per the discussion....LOL Several problems exist with studs. Most all studs have cut threads... Rolled threads are stronger. The Northstar head bolts are rolled threads. Heading the nut head on the bolt makes it very very strong. There is no failure ever reported in that area. Once installed and tensioned there is no functional difference between studs and bolts. Period. Any fastener engineer can tell you this. Just no reason for any difference. The column of the fastener , once stretched, is the load bearing member. The metallurgy of the bolt, the amount of stretch induced during tensioning and the bolt dimensions decide the strength...not the fact that it is a bolt or stud. Studs are used in high performance engines for two reasons....they can be make any size/lenght rapidly on demand since the threads are cut....and they eliminate wear in the female threads during repeated assembly/dissassembly of the engine, common in racing. Production engines are nailed toqether and the vast vast majority of them stay that way for the rest of their life until they are melted down.

BTW....in that same display of competitive engines there are no studs, either.....LOL LOL LOL

Just because the author has no background or knowlege of timeserts does not mean that they are inferior or will not work. Timeserts are an excellent product and have been well tested in development and in service in the Northstar head bolt application. I have seen tons of data on them and their performance so I can personally attest to the performance of the inserts. The fact that the application specific inserts were developed for the Northstar head bolt application and tested for that joint long before production of the engine started indicates that the repair is well founded and absolutely reliable.

The fact that the timesert is a solid insert and spreads the engagement of even ONE thread on the ID to the entire length of the OD makes the inserted repair extremely strong and dependable. The head bolt engagement into the insert (since it is hardened steel) is not nearly as important as the correct engagement of the insert into the block...which is why there is a specific Northstar insert and installation kit provided to ensure this if the repair is necessary.

Mr. gtm2u claims fall into the same category of most internet experts that are struggling to examine and explain something they know little about since they have never actually seen a real live Northstar engine apart and never worked on one themselves.....

GM copied a Lancia V6.....LOL LOL LOL LOL

If you want another opinion, call the owner of Cadillac Hot Rod Fabrications, Alan Johnson ( www.chrfab.com ) and ask him how many engines he actually timeserts or how many engines he builds with studs to "hold the heads on"....LOL Since he builds some 8000 RPM, 750 HP turbo charged and supercharged Northstar engines he MUST be having trouble with the head bolts, right....???.....wrong. Seems the same production head bolts that can "barely contain combustion" can barely contain the combustion of 750 HP in his race engines. Maybe you can enlighten him.

BeelzeBob
03-08-05, 12:44 AM
My personal experience is that after 30 years of driving all different makes and models, only a meticulously maintained Northstar Cadillac with under 50,000 miles has ever stranded me hundreds of miles from home, causing me to have to repair the POS in a hotel parking lot, finishing up at 2:00 AM.

.


Sorry you had a problem with the car...but....what kind of repair that you had the tools for in your trunk and was completed in a motel parking lot has anything to do with the discussion of head bolts and aluminum blocks...???

I agree with the erosion of market share and such....people have had decades to live with predomenently GM and domestic cars and have had plenty of time to experience one horror story/experience to drive them to the competition. Too bad they have not had too much time to live with the competition the same way and hear the horror stories from their dads and granddads, etc... After a few Lexus owners anty up after a timing belt replacement maybe they will never own another Lexus again and will buy GM. Same for BMW, Mercedes, etc..... Check the hate sites for other brands. There are always problems in all cars and they show up on the internet. Quite dwelling on Cadillac and Northstar and look around and prove me wrong.

As long as I am on THAT rant....I am personally pretty fed up with the Quality of US health care, for you doctors out there. After misdiagnosing my wife three times for a ruptured appendix and her almost dying I am ready to give up on US doctors as incompetent and useless and ready to switch to a foreign brand....guess what..???....they have a captive audience. Based on my experience living in houses I am also fed up with the quality of US home builders, for those of you in "the trades" out there. Wish I could buy a high quality Japanese house.....hmmm....another area with no quality control and no accountability because they have a captive audience. Wake up. The same thing that woke up the US automakers exists in many other areas...but those are areas that are not "global" so they have a captive audience. Think about it before calling the kettle black.....

BeelzeBob
03-08-05, 12:47 AM
Isn't it odd how all these horror stories of head gasket failures and such always happen on METICULOUSLY MAINTAINED CARS.... LOL LOL Meanwhile, I see hundreds and hundreds of high mileage Northstars driving around on the mean streets of Detroit that are clearly NOT maintained at all.... Maybe there is a lesson here. Just funny, that suddenly any and every car with a failure is "meticulously maintained" .... not just a used car that someone bought....????

dkozloski
03-08-05, 01:17 AM
Bbob, talking about meticulous maintenance. Back when I was in the missile racket everything was offloaded from the ships periodically and sent to the depot for inspection and repair. Everything came apart and was inspected and tested. It was all sent back to the ship and inspected and tested some more. Reliability was always a problem. Then the Navy shifted gears and said "Let's treat this stuff like a round of ammunition". At this point it was carefully assembled, inspected, and tested one time and sent to the fleet. They were told to leave it alone and don't mess with it. Reliability rates went through the roof. I would bet that from the looks of the average grease monkey you see fooling with your car there is a heck of a lot that gets done to the car that does more harm than good. The Air Force found that the inspection of wire bundles in aircraft introduced more faults than it prevented. Put the cars together, seal them up, and don't let anybody with tools near them.

dkozloski
03-08-05, 01:43 AM
Bbob, once again you are right about the difficulties of assembly with studs rather than bolts. Lycoming engines have crankcase through bolts screwed into one case half with very tight fits. These must be started into precision holes in the other half with great care because they act as the dowels that position the bearing saddles. Everything has to go together with no misalignment to prevent damage to the holes. I can't imagine this being done on an automobile engine line. Continental inserts the studs like dowel pins after the cases are together but the studs stick all the way through on both ends and then are nutted on both ends.
I have seen water cooled engines with cylinders separate from the crankcase that have bolts that hold the head on that go clear through the crankcase and out the bottom to hold the main bearing caps on as well. If memory serves me correctly the cylinder blocks were cut off of small block Chevys with a band saw and the crankcases were machined out of aluminum billet stock. I think the makers name is Gaertes, the finished product goes in a midget racer, and has the reputation of being the most bullet proof engine known to man.

Stoneage_Caddy
03-08-05, 01:48 AM
I have seen water cooled engines with cylinders separate from the crankcase that have bolts that hold the head on that go clear through the crankcase and out the bottom to hold the main bearing caps on as well. If memory serves me correctly the cylinder blocks were cut off of small block Chevys with a band saw and the crankcases were machined out of aluminum billet stock. I think the makers name is Gaertes, the finished product goes in a midget racer, and has the reputation of being the most bullet proof engine known to man.

isnt this the same setup as the old Jag inline six (as far as head bolts into the mains)?

the indy offy also comes to mind ..(seperate crankcase at least and bullet proof lol)

dkozloski
03-08-05, 02:09 AM
I think the Indy Offy had a barrel crankcase where the mains were built up around the crank and then the crank assembly went in through the end of the case and you put the rod caps on through hand holes in the case. I think this engine morphed through several lives as the Miller, Offenhauser, Meyers & Drake, and maybe one more. Meyers & Drake made most of the Indy Fords.

Stoneage_Caddy
03-08-05, 02:15 AM
oh , wow that thing is more odd than i thought it was ....

I read that since it had no real "cylander head" is how they ran the huge boost numbers on them in the 70s....

sorry im off topic everyone...

Spyder
03-08-05, 02:42 AM
Just for the record... ...I'm really enjoying this thread. Incredibly informative and a great read!!!

And even though I don't really have any idea what exactly dkozloski is talking about half the time(as far as personal experience), I still find it quite interesting. Keep it up ya'll!

dkozloski
03-08-05, 02:45 AM
Here is a link that will blow your socks off. What these people accomplished is beyond belief. Keep the dates in mind as you read the specs of their engines. http://www.milleroffy.com/

dkozloski
03-08-05, 03:09 AM
DR. Sanford Moss of GE, the man who invented the turbocharger in 1917, designed the superchargers that Harry Miller used and made it all possible. I was very good friends with a man, Chet Lincoln, that worked for Harry Miller when he was first getting started in California. Chet's family raised mules for the honest to goodness 20 Mule Teams that hauled the borax out of Death Valley.

dkozloski
03-08-05, 03:10 AM
You'll have to bear with me. This stuff just keeps popping into my head.

gtm2u
03-08-05, 05:28 AM
Regarding mr. gtm2u's comments.....

Actually, when the Northstar was designed the head bolt thread engagement was GREATER than the industry standard recommendations for bolts into aluminum. The Northstar head bolts provide more than 2 times engagement and the bolt length has been upgraded over the years to 2.5 engagement.
...
GM copied a Lancia V6.....LOL LOL LOL LOL

If you want another opinion, call the owner of Cadillac Hot Rod Fabrications, Alan Johnson ( www.chrfab.com (http://www.chrfab.com) ) and ask him how many engines he actually timeserts or how many engines he builds with studs to "hold the heads on"....LOL Since he builds some 8000 RPM, 750 HP turbo charged and supercharged Northstar engines he MUST be having trouble with the head bolts, right....???.....wrong. Seems the same production head bolts that can "barely contain combustion" can barely contain the combustion of 750 HP in his race engines. Maybe you can enlighten him.

I was hoping to have received an honest answer but judging from the tenor the intent was more at attempting to discredit my post. Maybe that works with most of the poeple that frequent this site but for all those who have the short bolts don't have the advantage of the 2.5x which you state are in fact being used.

The bolt was not of adequate length by your own admission since it was upgraded over the years to reflect what was still _not_ 2.5x the diameter.

Attempting to blow smoke just doesn't cut it, re-read your post where you state the threads are down to the cylinder bores is absolute hogwash and yet you state I've NEVER seen a Northstar engine. Get out of that office and take a look if you can figure out how to take the intake manifold off. As for elongation I don't think they had in mind for the threaded portion to stretch and yet this is exactly what I've measured.

Interesting that you compare a piece of "all-thread" and cut threads when we both know this is not what is used. Tell us what the tensil strength of the head bolts is and then provide the calcs that you suggest are adequate to withstand repeated loads in excess of 90,000 lbs with what safety factor. We are not talking about an engine producing .5 or .75 hp / cu in.

It is obvious you know nothing of Lancia, to compare what Fiat did to them and doors falling off to engine design is again just another smoke screen.

How is is possible that you do not keep abreast with the fastner industry who jumped on on that bandwagon of using torque angle have now reversed their thinking. But again an attempt to discredit me and then make the bold statement that each bolt will seal the gasket joint at 15 kilos.. gimme a bit more credit than that. Most assuredly this is not at max hp/torque for were that true why not use a 6mm bolt...

What I did read on the Internet was woefully inadequate and filled with urban legends and I'm sorry to say this post demonstrates a serious lack of knowledge of this and other products. I will take you up on your offer to take me through "the display" of Italian engines used in production line vehicles, I'll pay the air fare and expenses but expect to be reimbused should you discover that inserts are being used. To suggest that a CNC machine cannot be programed to install head studs is again just a smoke screen which is absolutely not factual. I do not claim to be an expert on Northstar engines but it is obvious that the little I have learned form first hand experience and the caluclations is more than the effort you have given them other than reading some possible circulated blurb. If you are in fact employed by Cadillac / Northstar you should hope the people that sign your check don't see what you have written for it falls mostly into what I consider urban legend and not that of a professional.

I've seen the name Alan Johnson on the Internet, even attempted to contact him at one time but didn't get the courtesy of a reply. Criminies Alfa Romeo was producing racing engines with 1500 cc that exceded 750 hp back in the mid to late 30's. Let me help you out that's 1 hp for every 2 cc so I'm not impressed.

It is unfortunate that the cheering squad has to hold your coat as if you were in a fist fight which I guess was all you needed to be goaded into this approach and the lip service to maintain some status among your followers. So tell us why was there a need for second repair? Why do I think you are in the under 35 age group...

If this is the best you can do don't waste my time for I've done my homework and paid my dues a long time ago which is more than I can say for the content of the response I received.

Cheers,
GTM2u

gtm2u
03-08-05, 07:08 AM
Here is a link that will blow your socks off. What these people accomplished is beyond belief. Keep the dates in mind as you read the specs of their engines. http://www.milleroffy.com/

Back in my rakish youth I worked with O.A. (Bunny) Philips of Bugatti restoration fame and his lead mechanic was Joe Fernandiz. The stories these guys would tell about their Indy exploits with Millers and Offy's would keep you in stiches for hours. Joe ran a Texico station at Pico and La Brea in Los Angeles until he retired and went back to work for Bunny where we met. One of the more interesting tales was that of a rod knock which developed mid Indy race. Since he and Bunny were competing for points he wasn't about to have a DNF. He takes the pan off and decides he doesn't have time to re-babbit the rod (you guys forget what's it's like to scrape bearings) for they didn't have inserts. So Joe always on a shoe string with his racing improvises by cutting the leather tounge out of his shoe and stuffing it in the rod so he could re-enter the race for the last two laps. I sure learned a lot in the 2 years I was with him but I just couldn't stand the fact the boss would go out and drink his lunch and then come back and jump on Joe's case about something. To see a grown man humiliated like this day after day was more than I could take so gave him a piece of my mind, hung up my apron and left. Still I can look back at some of those jobs I did such as hand scraping blocks and heads along with spot turning replacement firewalls using an 18' (foot) radial arm drill with some fondness. I never heard what happened to Bunny's Royale for he moved his shop to Solvang/Buleton area and into obscurity. Joe had seen it all and was a wealth of information including a starter which I have yet to see mentioned anywhere. This was before electric starters and the dangers of hand crank engines just wasn't acceptable for the laidies. This starter used an articulated running board which when stepped on repeatedly would pump up an air cylinder which was then released to crank the engine. I never knew all the mechanics but would love to see the drawings if not the real thing.

Yes those were the days of bean oil and chewing gum. :)

Cheers,
GTM2u

dkozloski
03-08-05, 12:45 PM
I've got an idea. Let's all back up a step, take a breath and start over. It's obvious that this is an excellent chance for all of us to learn something from each other. GTM2U, could you give us some background to kind of establish your credentials, so to speak? I'm retired after a long and varied career. I was a journeyman machinist in a custom machine shop at the age of seventeen. Since then I have worked at everything from nuclear powerplants to guided missiles and computers to managing an aircraft engine overhaul shop and finally retired as the facilities and ground equipment manager of a regional airline. Bbob is a very long time Cadillac Northstar engineer who has been in the program since it's inception. Give him a chance to explain where he is coming from. I think he was a little short with you because there has been a barrage of attacks lately from less than credible sources that he has had to defend.
Welcome to the discussion.

dkozloski
03-08-05, 12:57 PM
We really need some perspective here. Does anyone have any failure rate and failure mode data on the Northstar engine that they would care to share with us. I went through a seige of crankcase cracking controversy with aircraft engines that turned out to be a tempest in a teapot, driven by trial lawyers that seemed to favor the type of aircraft involved. Until we have some hard data to put alongside the competition all we have is an argument comparable to UFO's and astrology.

BeelzeBob
03-08-05, 12:57 PM
I was hoping to have received an honest answer but judging from the tenor the intent was more at attempting to discredit my post. Maybe that works with most of the poeple that frequent this site but for all those who have the short bolts don't have the advantage of the 2.5x which you state are in fact being used.

The bolt was not of adequate length by your own admission since it was upgraded over the years to reflect what was still _not_ 2.5x the diameter.

Attempting to blow smoke just doesn't cut it, re-read your post where you state the threads are down to the cylinder bores is absolute hogwash and yet you state I've NEVER seen a Northstar engine. Get out of that office and take a look if you can figure out how to take the intake manifold off. As for elongation I don't think they had in mind for the threaded portion to stretch and yet this is exactly what I've measured.

Interesting that you compare a piece of "all-thread" and cut threads when we both know this is not what is used. Tell us what the tensil strength of the head bolts is and then provide the calcs that you suggest are adequate to withstand repeated loads in excess of 90,000 lbs with what safety factor. We are not talking about an engine producing .5 or .75 hp / cu in.

It is obvious you know nothing of Lancia, to compare what Fiat did to them and doors falling off to engine design is again just another smoke screen.

How is is possible that you do not keep abreast with the fastner industry who jumped on on that bandwagon of using torque angle have now reversed their thinking. But again an attempt to discredit me and then make the bold statement that each bolt will seal the gasket joint at 15 kilos.. gimme a bit more credit than that. Most assuredly this is not at max hp/torque for were that true why not use a 6mm bolt...

What I did read on the Internet was woefully inadequate and filled with urban legends and I'm sorry to say this post demonstrates a serious lack of knowledge of this and other products. I will take you up on your offer to take me through "the display" of Italian engines used in production line vehicles, I'll pay the air fare and expenses but expect to be reimbused should you discover that inserts are being used. To suggest that a CNC machine cannot be programed to install head studs is again just a smoke screen which is absolutely not factual. I do not claim to be an expert on Northstar engines but it is obvious that the little I have learned form first hand experience and the caluclations is more than the effort you have given them other than reading some possible circulated blurb. If you are in fact employed by Cadillac / Northstar you should hope the people that sign your check don't see what you have written for it falls mostly into what I consider urban legend and not that of a professional.

I've seen the name Alan Johnson on the Internet, even attempted to contact him at one time but didn't get the courtesy of a reply. Criminies Alfa Romeo was producing racing engines with 1500 cc that exceded 750 hp back in the mid to late 30's. Let me help you out that's 1 hp for every 2 cc so I'm not impressed.

It is unfortunate that the cheering squad has to hold your coat as if you were in a fist fight which I guess was all you needed to be goaded into this approach and the lip service to maintain some status among your followers. So tell us why was there a need for second repair? Why do I think you are in the under 35 age group...

If this is the best you can do don't waste my time for I've done my homework and paid my dues a long time ago which is more than I can say for the content of the response I received.

Cheers,
GTM2u


Your post desires to be discredited as it is full of misinformation and inuindo....nothing but.


I don't understand where you keep coming up with the "short bolts" idea....??? The Northstar bolts are quite LONG....always have been..... Simply looking at the block and the bolt holes one can see that the bottom of the head bolt threaded area is at the bottom of the cylinder wall. What part am I misrepresenting or missing....????

If you think I sit at a desk and have never seen a Northstar engine you are woefully mistaken....LOL....LOL...LOL I bet I can take one apart and put one back together blindfolded with one hand faster than you can and mine would run when I was done....LOL

Can't take the intake manifold off...???....uhhh...what is to understand. I can have the intake off, change the starter or put it into your hands and let you see it and reinstall it on a Northstar in the car, drink a beer and get it done in less than an hour easy. Have YOU ever taken one off...??? Besides, I don't need to take the intake off to see what is going on...I see thousands of them built from scratch every week.

Plan your trip and airfare to Detroit, pal. Plan on buying the tickets yourself. Glad to show you the facts. BTW....there are more than just "Italian" engines in the mix.....LOL..... We are not talking about some antique 1960 one off racing engine , here, but a whole series of current production aluminum engines for passenger cars. Trust me and save some dough on the plane ticket....they do not use thread inserts anywhere in the block or heads or ANYWHERE.

You compart age old Lancia racing engines that had to last all of, what, 2 hours or so to a modern production engine that runs in passenger cars, gets good fuel economy, starts in all kinds of climates and temperatures, meets emission levels of the most stringent level and runs for hundreds of thousands of miles.....??? Does the phrase "apples to oranges" mean anything to you..??? Besides...really now....a 1.5 liter Alfa Romeo making 750 HP in the 30's....???....LOL.... Sorry about my crack about the doors falling off....just that , if they cannot keep the doors on I have a hard time taking their engines seriously.

What is the comment about all-thread supposed to mean...??? Look at the high strength studs used for racing engines closely. They all have cut threads. As you mentioned, it is easy and inexpensive to have the steel rod of the correct metallurgy around. It is cut to length, threaded on each end and used for the studs. (I am not making this up) What is the advantage of that approach other than the items I mentioned??? No one (but you) mentioned all-thread rod. The head bolts used in the Northstar are , in effect, forged with the heads forged in place and the threads rolled into the parent metal of the bolt. This is a far stronger piece with less stress riser potential than any stud cut to length and threaded.

I already provide examples and loads. The 40 kilo newton load per head bolt is real. Do the math yourself. Since no one has EVER mentioned a broken head bolt the facts indicate for themselves that the bolts have enough safety factor to withstand the load easily. The fact that the sealing system is used on engines with MUCH greater output is a practical example that the fastening system is ample. I mentioned the fact that the joint can seal with as little as 15 kilonewtons of load per bolt to establish and illustrate some level of the safety factor that the joint has. sorry you could not grasp that. Actually, the joint could likely be held with 6mm bolts...but they would have NO safety factor....the larger bolts tensioned to 40 kilo-newtons provides significant safety factor for head sealing, combustion loads and thermal fatigue of the joint.

Since when has the fastening industry abandoned torque-angle strategy...??? just because you missed mentioning it in your comments (indicating that you do not really know anything about the Northstar engine) does not mean that it is not alive and well and being used on a daily basis on production lines across the country...which, in fact, it is. Torque angle tensioning strategy is a far more accurate way of tensioning bolts than simple torque or any other means and is the standard of the industry for tensioning critical bolts in blind holes. Torque angle tensioning has NOT been abandoned by the fastener industry least someone reading this be mislead by your comments.

If you are not claiming to be a "Northstar engine expert" then why exactly are you attacking the design features of it...which you apparently know little to nothing about. I will go out on a limb and say that I AM a Northstar engine expert of sorts....having worked on the engine since the early days of it's design and all during it's run in production todate. Your general statements and comments do nothing but arouse suspision and distrust. You do not attack anything with specifics or facts or calculations of your own...but then expect them of other people...??? Doesn't work like that. YOU prove the design is wrong if you are not a "Northstar expert" and provide specific items to refute and then I will do the same.

Exactly what does having a "CNC machine install a stud" have to do with the discussion. Regardless of whether a CNC machine or a hand installs the stud the act of installing a cylinder head over 10 studs, sticking up 6 inches in the air, simultanseously is very hard to do. Only someone who has never tried it would make it sound easy or practical.

No doubt that you are very expert in your field.... Your posts, however, are vague and full of inuindo and compare apples to oranges. You are getting direct feedback on the issues that you bring up.

If you cannnot get ahold of chrfab to understand what they are doing or to get feedback on the capability of the Northstar head bolt system and it's ability to handle far more cylinder pressure than the production engine makes then you are just not trying. Much easier to punch the keys on that keyboard and stare at that screen, eh...??

This discussion with you is trivial to me. You mention haphazard facts and allegations and then "demand" a technical treatise to refute your claims. Just don't have the time. I don't need to prove that thread inserts are not used in other engines...you can find out for yourself instead of making it out that it is my responsibility. I also could care less that you are convinced as you obviously have another agenda in your posts....I just want others reading the thread to understand that your posts are not factual and that there are significant errors and misinformation in them so that THEY are not mislead.

Sorry if all of this is not professional enough for your. Your attack on the Northstar engine is weak and ill informed which is not very "professional" either. As for the guy that signs my paycheck, I'll be sure and tell him that you do not think that I know what I am doing...LOL

Stoneage_Caddy
03-08-05, 01:00 PM
Here is a link that will blow your socks off. What these people accomplished is beyond belief. Keep the dates in mind as you read the specs of their engines. http://www.milleroffy.com/
LOL ..thankx dude , went thrut he site and found some books ive been looking for , got the titles and ran them on amazon ....

Offenhauser: The Legendary Racing Engine and the Men Who Built It
The Marvelous Mechanical Designs of Harry A. Miller
Indy's Wildest Decade: Innovation and Revolution at the Brickyard (60s)
Novi V-8: Indy Cars 1941 Through 1965 (Ludvigsen Library Series)

i may not have lived then but the Offy , Novi and turbine always intruiged me ...should make for some good reading

I should make a "INDY" thread somewhere

dkozloski
03-08-05, 04:31 PM
Bbob, I only have one bone to pick with you. I think you would have a hard time finding a stressed stud or through bolt in an aircraft engine with cut thread. Rolled threads on cylinder base studs on Pratt & Whitney engines go back to long before WWII. Even the studs that hold the exhaust stacks on are rolled thread. Studs with rolled thread are easy to find if you know where to look.

gtm2u
03-08-05, 06:18 PM
I've got an idea. Let's all back up a step, take a breath and start over. It's obvious that this is an excellent chance for all of us to learn something from each other. GTM2U, could you give us some background to kind of establish your credentials, so to speak?
...
I think he was a little short with you because there has been a barrage of attacks lately from less than credible sources that he has had to defend.
Welcome to the discussion.

I'm semi retired and too old to be a fanatic about anything. I have worked on every major imported car that has come into the US. I was a pre-med drop out when money and personal problems got in the way, spent a few years as a research aide and lab tech. I switch vocation for avocation and found I was more than competent and could make a good living twisting wrenches at dealerships and indepedents including my own specialty shop. I have long since learned that every maker has it's own can of worms and in this case it's the N*/s head bolt which I believe can be corrected yet in the 10 years of production there have been 3-4 attempts by the factory to remedy the problem. I've not condemned the engine with broad sweeping brush strokes for I think it's been well designed and the performance is well above average especially as fitted to a large car.

Back to my life experiences: because Detroit had built large heavy engines, massive cars and seemed to be slow with experimenting and innovation I found the imports to be more of a challenge for they were all trying new things. Sometime in early '60's I designed the first transistor ignition driven off the flywheel which eleminated the distributor unfortunately I never applied for patent and the idea was used some years later at Indy. Being full of piss and vinegar I also volunteered my weekends with SCCA as tech inspector including teardown supervision for illegal mods. This also allowed exposure into F1 as we had the staff to conduct races that met FIA's requirments. Thus I got to see cars and components which never were intended for production applications. I saw what the competition could never see which made things reliable and go fast. I even had the honor of doing same in Mexico and Italy because I was fluent enough in technical terms to be conversant. I turned down an invitation to be lead mechanic for Jim Hall and Hap Sharp because I didn't want to move to Texas.

I'd not given up on academics and took night school classes in areas that interested me. An opportunity came along to teach auto mechanics in night school so I got my provisional teaching credential thinking it might prove useful since I had never considered twisting wrenches as a life long ambition. I also got my Master Mechanic license with NIASE/ASE but as you get older twisting wrenches takes it's toll thus became Service Manager for a large Japanese dealership with 25 mechanics. I had already gone through 1 marriage of less than 5 years and started a second when my interests took me into sailing and yacht design where I offered my weekends helping a friend build an egg-shell kit until I was in a position to do same. My auto racing interests wained so had time to start my own but selected a recognized IOR hull designed by Allan Gurney. The logic was that the same equipment goes into a sailing yacht no matter what the construction medium thus pay the extra bucks for the egg-shell made by one of the top builders. Since the long range plan was to do a circumnavigation I designed a lot of custom hardware which I then had cast and through a friend had access to a machine shop that had done all Corvette models since day one until the 80's. (I can state that now since the owner retired and I don't know who does their model work) The order of well kept secrets is the government, the toy industry, and Detroit's model subcontractors. :) Dealerships include some with combined products but probably forgotten a few.Austin, Cooper, BMC, Triumph, Rolls Royce, Rover, Lotus, Porsche, Audi, VW, and Nissan. My own shop included Lancia, Ferrari, and Maserati. My first car age 13 was a '36 Buick which my brother and I paid $8. My first motorcycle was 6 months earlier and given to me in a gunney sack so I can say I've been riding and driving for over 50 years. The Buick was the first valve grind and the bike my first 2 cycle.

The circumnavigation never happened though we campaigned the boat for a few years with local races. Crazy stats for I had joined a yacht club with a good racing history and found that there were 6 people who I had known back in my research days at JPL, Cal-Tech, and SCCA. Anyway the bottom fell out of boats and property went sky high which left us raising 2 kids for 20 years aboard our yacht. Somewhere in all that I became an associate member of SAE and the Adventurer's Club, left the automotive industry from burnout and confining myself to things which are not making a lot of money.

I don't know if that's what you were looking for when judging character and qualifications, it is some of my life experiences. While I have no intention of getting into a pissing contest I certainly can hold my own and have little tolerance for those who for whatever reason are willing to misrepresent factual information repeatedly. I've had the great fortune of knowing some of the best engineers in the US and have never seen this nonsense, they don't have egos to flaunt and they don't have axes to grind. I aso know it's sheer folly to attempt a discussion with those who do. I will continue to confine myself to those who are an authority on the specifics of my quest for the truth but I sure _ain't_ going to find it here.

Cheers,
GTM2u

Stoneage_Caddy
03-08-05, 06:34 PM
I turned down an invitation to be lead mechanic for Jim Hall and Hap Sharp because I didn't want to move to Texas.

You coulda worked on the Vaccum cleaner can am car ????? or the first ground effects indy car ????

wow ....

BeelzeBob
03-08-05, 06:46 PM
Bbob, I only have one bone to pick with you. I think you would have a hard time finding a stressed stud or through bolt in an aircraft engine with cut thread. Rolled threads on cylinder base studs on Pratt & Whitney engines go back to long before WWII. Even the studs that hold the exhaust stacks on are rolled thread. Studs with rolled thread are easy to find if you know where to look.


We were talking about automotive engines and specifically the Northstar when the issue of studs came up....

I realize that application specific studs are readily available for the intended applications with rolled threads. The common aftermarket studs used for many performance engines to offset the wear and tear on threads for repeated teardowns and rebuilds are most commonly cut threads...just look at them and the major diameter of the thread compared to the shank of the stud. That is why they are readily available and relatively cheap...they have cut threads that require no special tooling to make. Rolled thread studs require specific blanks and specific tooling to make...not cost effective or practical for a set of 20 or 30 studs.

The implication in the earlier post that somehow studs were superior or stronger due to metallurgy or whatever imagined property is what got the discussion on studs started and I still have not seen anything factual to back it up....

dkozloski
03-08-05, 07:31 PM
Every make of car has some kind of urban myth about it. I remember spending an awful lot of time going through junk yards looking for flathead Ford V8 blocks that weren't cracked through an exhaust valve seat and down the cylinder. 216 Chevy engines were a dime a dozen but good transmissions were hard to find. Flat head Chrysler products had rod knocks. Studebakers smoked and burned oil. The front end looked funny and collapsed on flat head Oldsmobiles. The rear cylinder on straight eight Buicks did a continuous slow cook. I've seen flathead Fords with aftermarket aluminum heads that had the studs so tightly corroded into place that the engine would run just fine with no nuts on the studs at all. I had to make a hollow drill that would go down around the studs and drill the corrosion out to get the heads off and then I found the blocks cracked anyway. That was what is called the good old days.

gtm2u
03-08-05, 07:45 PM
Bbob, once again you are right about the difficulties of assembly with studs rather than bolts. Lycoming engines have crankcase through bolts screwed into one case half with very tight fits. These must be started into precision holes in the other half with great care because they act as the dowels that position the bearing saddles. Everything has to go together with no misalignment to prevent damage to the holes. I can't imagine this being done on an automobile engine line. Continental inserts the studs like dowel pins after the cases are together but the studs stick all the way through on both ends and then are nutted on both ends.
I have seen water cooled engines with cylinders separate from the crankcase that have bolts that hold the head on that go clear through the crankcase and out the bottom to hold the main bearing caps on as well. If memory serves me correctly the cylinder blocks were cut off of small block Chevys with a band saw and the crankcases were machined out of aluminum billet stock. I think the makers name is Gaertes, the finished product goes in a midget racer, and has the reputation of being the most bullet proof engine known to man.

I know little about aircraft engines but Porsche & VW machined the case halves and installed locator dowel pins along with some subordinate through bolts before installing studs. Both had their share of torn threads and crancase distortion so bad that you couldn't crank them in cold weather.

I failed to mention Jag but my initial work experience only remembers the 140-150 series and into the E types and don't remember "cylinder blocks". Some Bugatti, and if memory serves Offy, and Miller engines used cylinder blocks which I define as a one piece crankcase which may or may not house a roller crank. A cylinder block which included the head and a flange which bolted to a flat machined surface on the crancase which elimenated head bolts. The lower portion of the cylinders extended into the crancase and the upper portion was included in the water cooling jackets. The combustion chamber and valve seats were all part of that casting. I don't remember them having valve seats and I think the guides were also part of that casting. I had the dubios honor of doing all the valve jobs on the type 30 engines for my had was small enough to fit inside the cylinders to do the many fittings and lappings. These engines were prone to combustion chamber cracks from spark plug hole to valve seat which could not be stopped with sodium silicate treatment. For those if the customer was willing we machined valve seat inserts working from the inside the cylr but driven by that huge radial arm drill on the top. Once the new seat was in place the engine was assembled on the breakin stand and given the sodium silicate treatment over 2-3 days mixed with short running periods and then using the sodium silicate again. Final was 8 hours of running at various speeds with the transmission attached.

I have seen cylinders as all one casting and then heads set on top but can't remember who the maker was. I do remember making some head gaskets from copper and asbestos by hand when we couldn't find a ready made item which could be adapted but again memory escapes which engines.

Multi part roller cranks were fitted through the cylinder block opening in the crankcase and took a full day to assemble them for it was like building a complex Tinker Toy set inside a bottle. I remember receiving one engine from Japan that the owner had taken apart and couldn't get back together. Nothing was marked so we spent 2 days trying all the possible combinations of journals, mains, bearings, counterweights and pins to make it a 4 cylr engine. Loads of fun. :)

Cheers,
GTM2u

BeelzeBob
03-08-05, 07:56 PM
BTW...if anyone was following the exchange between gtm2u and myself....the subject of the load on the head bolts came up and gtm2u maintained that the head bolts, as installed, could barely contain compression based on "his calculations"

Just out of curiousity and satisfy a private message I received consider the following....

The Northstar engine has a bore of 93 mm or about 3.66 inches. This equates to an area of about 10.52 inches sqaure. If combustion pressures reach 1500 PSI that would then exert a force on the head of about 15,780 pounds. In otherwords...the combustion pressure of 1500 psi (this is a high number and is only seen instantaneously in any case) would exert a force on the cylinder head of almost 16,000 pounds trying to blow it off.... or....the head bolts must contain a force of 16,000 pounds to hold the head on. This is arrived at by multiplying the area of the head in square inches by the pressure in the cylinder in pounds per square inch.

The tension in each head bolt is about 40 kilonewtons or 40,000 newtons when tensioned properly...i.e...torqued and angled. That is the load on each bolt from stretching the bolt into place. 40000 newtons is about 9000 pounds of force when converted from metrics. 9000 pounds X 4 head bolts per cylinder is about 36,000 pounds of residual load to handle the 16,000 pounds of force from combustion.

As I indicated in my example from past experience the head bolts can seal with as little as as 15,000 newtons of load on each them. This equates to about 3400 pounds of force. 3400 X 4 head bolts per cylinder is 13,600 pounds of force which is just below the "high" estimate of 16000 instantaneous pounds of force at combustion. Just about the point that you would start to see head gasket combustion leakage.

Basically, this indicates exactly what I said in my discussion with gtm2u. The head bolts exert plenty of load to seal the combustion chamber and even at the very very low end of clamp load, the 15 Kn figure by memory, the load is sufficient to just barely start to leak from the instantaneous force from combustion. The proper clamp load of 40 Kn per bolt has a safety factor of 2.25 which is plenty for a mechanical device like this.

The 40 Kn of load from the head bolts has been verified countless times using Raymond Gage sonic bolt testing equipment that allows the stretch of bolts in blind holes to be measured accurately. In fact, once weekly, an engine is sent thru the production head bolt tensioning equipment with ground head bolts set up for the Raymond Gage sonic measurements and the proper bolt stretch with the production torque-angle spec is confirmed to verify the production specs are indeed providing the correct bolt tension of 40,000 newtons of load.

To put the cylinder pressure number I used of 1500 PSI into perspective....the average pressure in the cylinder of a 440 HP supercharged Northstar is about 250 PSI. That would be the average number for the entire power stroke. The peak number at peak pressure for just an instant in time is closer to 1200 PSI. I just used 1500 PSI as a ballpark number to be on the high side.

Not much else to say on this......

dkozloski
03-08-05, 09:04 PM
The British liquid-cooled Napier Sabre 24 cylinder sleeve valve engine was the most intense aircraft engine ever built. At 2200 cu.in. displacement it turned at up to 5500RPM, and ran at BMEP's approaching 500PSI before showing signs of strain. The cylinder heads were solid copper to disperse the heat and silver was comtemplated for later versions. On one test it was run at 4500H.P. and 5500RPM for more than 200 hours straight without shutting it down. How would you like to pay that fuel bill. from "The Power to Fly" by L.J.K. Setright. The limiting BMEP on air-cooled American radial engines was about 180PSI. I see the Northstar can run at about 250PSI.

blb
03-08-05, 09:23 PM
I think most of us agree, that on paper, the Northstar seems like a well designed engine.

But somwhere along the way, from the design on paper to the build of the engine assembly, something is going wrong in some cases. Maybe a small percentage of the purchased parts don't meet the design specifictions. (ie: material strength or hardness, thread depth, etc.) Maybe a small percentage of the headbolts aren't being torqued properly on the assembly line by the UAW. Maybe there's a problem with inconsistencies in the headgasket material. Instead of dwelling on only the design as it exists on paper, I would love to hear about some of the research, investigation and problem solving techniques that have gone into figuring out ways to improve the headgasket/headbolt/block thread issues on Northstar motors from a manufacturing perspective.

I recently had an opportunity to speak to a technician that has worked at a suburban Philadelphia Cadillac dealer for the past six years and he tells me that they average 3 to 4 Northstar Headgasket jobs per month. This particular dealership employs 11 full time technicians to give you an idea of the size and volume of the dealership. Many (about half in his estimation) are being done on vehicles under 5 years old. Folks, that close to one every week. He also tells me that two of the neighboring dealers in the area won't even attempt a headgasket/timesert repair. They will only replace engine block assemblies. There's more to this issue than can be blamed on improper maintenance.

There was a young Cadillac technician that used to visit this site from time to time that had similar experiences.

I really don't believe that the headgasket issues are as isolated as some on this site would have us believe.

I would be very interested to hear if any kind of log is being kept by GM in an attempt to document the percentage of headgasket failures on Northstars and what kind of work is being done to discover the root cause of the failures. Or, on the other hand, is GM still taking the positon that there is no problem to investigate?

dkozloski
03-08-05, 09:32 PM
Bbob, what happens to cylinder pressures in a Northstar when the engine is in dentonation. Many years ago in Fairbanks a DC-6 was refueled with jet fuel rather than the correct Av-Gas. When it hit the ground behind University Park School there were a good number of the cylinder heads that were opened up like melons and hanging from the pipes and wires.

BeelzeBob
03-08-05, 11:01 PM
There are a lot of head gasket failures showing up on the older model cars based on reports from this forum... I guess the "weak link" by default is the head gasket that starts to fail thru thermal fatigue, thermal cyling from cold starts, age and corrosion. Sooner or later something is going to start to weaken. Seems like an awful lot of the engines have way over 100K miles on them, though. There are some sooner but a lot of them are at high miles based on the info from this forum and the field.

Surprisingly, head gasket sales thru GM service parts are not "thru the roof" as one might expect based on the conclusions of the forum..... Since these engines are out of warranty the best indication of a serious problem in the field is the sale of repair parts...like the head gasket. No alarms in that respect have been tripped indicating to me that , while there are replacements going on, the overall number is fairly low considering the population of cars out there.

Keep in mind that a disproportionate number of failures will show up on this and other forums. As has been discussed many times, most of the forum members and people posting tend to do it because they have had or are having a problem...not because they are driving around blissfully happy. Even with the large number of members of this forum they still represent a very tiny fraction of a percent of the Northstar owners out there...and a very unscientific sample at that.

Given enough time and miles something is going to start to weaken in any engine. A Lexus engine will start to loose the timing belt at 100K or so, guaranteed. A Northstar might need a head gasket at that miles..... take your pick. I see it as an area for constant monitoring and improvement if the joint can be made more robust but not something that is epidemic or a low mileage failure.

The head bolts and holes are less of a concern to me than the head gasket itself. I really doubt that the bolts are simply pulling out in most cases. Hard to belive that the engine can go 150K and THEN the head bolt threads strip.....hmmm..... I suspect in most cases the head gasket starts to develop a crack in a fire ring from fatigue and/or corrosion and the head gasket starts to leak. At dissassembly some of the head bolt female, aluminum threads are damaged removing the bolts and repair is necessary. That is what the timeserts are for. It always looks like the bolt "just stripped" because the aluminum threads come out with the bolt but, if the joint had not been disturbed, the threads would have been fine. Just my 2 cents...certainly not any official position.

BeelzeBob
03-08-05, 11:11 PM
Bbob, what happens to cylinder pressures in a Northstar when the engine is in dentonation. Many years ago in Fairbanks a DC-6 was refueled with jet fuel rather than the correct Av-Gas. When it hit the ground behind University Park School there were a good number of the cylinder heads that were opened up like melons and hanging from the pipes and wires.

Same as in any engine....you see a tremendous, instantaneous spike of 500 PSI above the existing cylinder pressure that "rings" the chamber. Given continuous, heavy detonation the severe pressure spike can erode material from the head/combustion chamber and/or piston crown causing a stress riser and failure. It is always hard to predict how any given engine is going to fail with detonation. I have seen the SC Northstar engine run at full throttle, 6400 RPM with continuous light to moderate detonation deliberately induced with no problem....until after about 8 hours of continuous running accumulated and then the ground electrode from one of the spark plugs cracked off. That is not an unusual event for detonation. A large radial aircraft engine with severe detonation at heavy loads would likely come apart pretty quickly. There was a situation about 8 or 10 years ago when a delivery of leaded 110 aviation fuel was mixed up in a pipeline and lower octane fuel was pumped into a lot of light aviation aircraft as a result. There were several emergency landings due to loss of power from engine failure and a fatality if I remember correctly. The oil company responsible paid to have a number of engines torn down for inspection for damage..... Not sure of all the details but I do know it happened. Aircraft engines tend to be calibrated much closer to the margins in many cases since the use profile is much more carefully controlled and the fuel source is (supposedly) known and controlled. So the engines have little or no tolerance for lower octane fuel, especially military aircraft that tend to sacrifice longevity and cushion for low octane fuel for performance. This is especially true if the detonation leads to the spark plug or something else in the chamber overheating and becoming an ignition source leading to preignition. The preignition will almost instantly take out the engine with holes in the pistons the most common failure. Since this is pretty catostrophic the loose parts quickly escalate into much worse collateral damage.

I have never seen head gasket damage causing head gasket failure due to detonation per se. You can often see the effects of detonation on the head gasket as the fire ring in the area of the exhaust valves will be pounded into a concave surface in the area of the detonation. Even with the pounding the head gasket is fine and the high pressure spike has little or no effect on the head gasket sealing as the duration of the pressure spike is so short in time that it practically doesn't exist except to set up the shock wave.

dkozloski
03-08-05, 11:36 PM
A small aircraft engine can fail in as little as 30 seconds of dentonation. The symptoms you see on teardown are virtually no combustion chamber deposits and the edge of the piston above the top ring looks like a mouse has been gnawing on it. Either the head blows out of the piston or the piston melts from the crown down through the ring lands to the skirt. I have seen both failure modes. The experts told me that the aircooled engines encounter heat overload much sooner than an automotive liquid cooled engine. There was a refueling incident at Deadhorse, Ak where they had one refueling hose hooked to two tanks with a couple of valves. Someone refueled a bunch of planes with both valves on which gave a 50-50 mix of Av-Gas and jet fuel. Every engine failed in flight except for one very clever pilot. When he was advised of the situation he immediately climbed the plane to less dense air which gave him an over rich mixture that both cooled the engine and increased the octane rating of the contaminated fuel. I got the job of repairing his engine. There was no damage found but the oil company paid for all new parts from the crankcase out anyway.

gtm2u
03-08-05, 11:55 PM
I think most of us agree, that on paper, the Northstar seems like a well designed engine.

...

I recently had an opportunity to speak to a technician that has worked at a suburban Philadelphia Cadillac dealer for the past six years and he tells me that they average 3 to 4 Northstar Headgasket jobs per month.
...
This particular dealership employs 11 full time technicians to give you an idea of the size and volume of the dealership. Many (about half in his estimation) are being done on vehicles under 5 years old. Folks, that close to one every week. He also tells me that two of the neighboring dealers in the area won't even attempt a headgasket/timesert repair. They will only replace engine block assemblies. There's more to this issue than can be blamed on improper maintenance.
...

I really don't believe that the headgasket issues are as isolated as some on this site would have us believe.

I would be very interested to hear if any kind of log is being kept by GM in an attempt to document the percentage of headgasket failures on Northstars and what kind of work is being done to discover the root cause of the failures. Or, on the other hand, is GM still taking the positon that there is no problem to investigate?

I too have encountered similar numbers from local Cadillac dealers for pulled thread issues. The problem, however, is not confined to those years if current surveys are to be taken other factors must be considered. The factory recommended repair time is on the order of 21-23 hours to do the job as specified. They don't turn this over to trainee staff for you just can't trust a kid with a drill and tap in hand much less reading a vernier caliper.

Those that were lucky to get some factory assistance in parts and/or labor considerations will have had the dealership perform the job. What is not being considered is nobody in their right mind is going to spend $3,000-$4,500 for a repair on a car which can only be sold for $2,000-$3,000. I see no way to inventory head gaskets sold from dealer and independents so you can't get an accurate picture. DVM might provide some stats on cars being sent off to wrecking yards but we don't know exact details for them being trashed. I'm sure we cannot get records which show units sold vs current registration for any particular state if even that would be meaningful.

Here we are with a 10 year old car which started out life in the $35,000-$40,000 price range reduced to less than 10% of it's value in 1 decade. So what is happening to these Northstar powerplants, what I am reading and hearing is they are being converted to off road use such as high performance sand buggies with a large numbers being kept in Mexico. I have been working with a stud maker who may produce a repair kit but have not been able to get real info from Cadillac which will guide in the solution. I've had to repair many head bolt threads over the years, those which warranted repairs were usually from radical overheat caused by customer neglect. The bottom line is while those who profess to have answers are not living in the real world.

Until some crusader with a vast law library and staff is willing to take on Cadillac I doubt anything will be achieved except the dismissing hands of magic we have seen. Blame it on everything but the people who designed it... Hey "if you can't take a joke you shouldn't have bought one."

Cheers,
GTM2u

Loose screw
03-09-05, 06:19 AM
Just one tid bit, a possiblity, concerning the N* head bolts threads failures. Many years ago I worked on a few Mazda rotary engines and read about their use and problems in racing. It is an interesting engine with it's own set of challenges. An engine made of sections that is held together with a large number of very long bolts if I remember right they were about 14 inches long. They went through the many section and into the thread of the cast iron front section. The many bolts appiled a great a force clamping the whole engine together, except the front cover and oil pan which had their own small fasteners. The interesting thing that they found out about the bolts was - they worked fine for nomal use and occasional blasts to 7,500 rpm range but in racing the engine would run much higher and on some track run contiuosly at the 10,000 rpm and could run many races without having to be torn down. But in racing an unexpected problem was found - the engine passing high rpms range changes vibration and would it matched the bolts frequency breifly or over and long period of time but when it did the bolts would vibrate, a little, but it was enough to cause a failure at their waekest point which at the end near the threads. In racing the problem was solved by appling a vibration dampening coating to the long bolts (a thick sprial bead of RTV). The engine had been extensively factory tested and run on dynos in race shops but there is no test like the real world and time and it wasn't until the engine had been in public use for several years that this and other problems were learned and later addressed by the factory.

Though it is more likely that something else is occuring with the Northstar head bolts threads, like thermal cycles. But still, could a vibration be occuring at certain RPMs that would be picked up by the bolts and migrate down and contribute over a long period of time to weakening the weakest point of the N* headbolts - the softer and weaker threads in the bock.
Just a thought, a tid bit, not a claim, so please relax.

dkozloski
03-09-05, 12:36 PM
I saw some data that the Mazda RX-7 rotary motor went from being the worst engine on the market to the most reliable engine ever put in a car. Before they were discontinued only 0.1% ( 1 in 1000) of all owners reported engine trouble of any kind, for any reason, including running out of gas. The average milage where the trouble was reported was 168,000 miles. If I remember right CU is the source for this info. FWIW, I have seen several references that state that the europeans found that under certain conditions the DexCool type anti-corrosion package can attack the materials in modern head gaskets. I think the Swedes have done some work in this area.

1996deVille
03-09-05, 12:41 PM
...and now for a little different twist.

I'm no where near the expert of those posting on this concern so far. I rebuilt a 1979 deVille years ago, the old 425, with great results. My background is working in the Boeing Model Shop and building musical instruments - so I'm not an engineer.

I've got 113K on my '96 deVille. For the 45K I've had it the motor has been wonderful. My concern isn't that the head gasket will eventually go - they ALL will at some point, or the material/s used in the design of the engine. My frustration is that a person must lift the body away from the engine to get to the head gasket/s.

The first job I did on this car was to replace the blower motor for heat and A/C. I knew I was in trouble when I saw "cut here" molded into the plastic around the original unit in the firewall. I called the dealer and asked if this was literally true - he said it was unless I had a hoist to lift the car so the fwd motor mounts could be loosened and the engine rolled forward so the fan would clear the rear valve cover. Sigh...

My point is this: I don't mind doing the work necessary to keep my autos running EXCEPT when the design of the car makes getting to the problem a larger concern than doing the repair.

The quote to replace my fan was $700 plus parts, for a grand total of $1000.00. For a blower motor... I cut the firewall, its in and working, but this should have been a simple one hour job.

The reality of the situation is that the newer cars, European and Japanese as well, are built with a different mind set. They are not designed with maintence in mind - the same holds true for the older cars, but the technology of the day made repairs easier.

I guess the point is to determine the true cost of ownership and live with it. The days of twisting wrenches on your own car is quickly becoming a thing of the past...

The Northstar does get up and go... and I've had 27.2 mpg on several long runs... not bad, not bad at all!!!

My dad's old 1968 GMC is my next ride - 327 with a TH400 and a Spicer rear end. I'll post some pics upon restoration...

dkozloski
03-09-05, 12:51 PM
I had a 1966 El Camino that the factory (Helms) service manual said that you used a 2x4 to pry the fender inner panel out of the way to change the blower motor. 1954 Mercuries were put on the market with no way to get the oil filter off unless the whole car was raised on a lift, the steering wheel cranked to one extreme, and then one wheel was manipulated with a floor jack. On a Chevy Monza you had to loosen the motor mounts and raise the engine to get some of the spark plugs past the steering gearbox. After the mounts got old you could pry the engine high enough with the 2x4 you had left over from the El Camino to access the plugs.

BeelzeBob
03-09-05, 01:00 PM
Most any of the transverse FWD powertrains are easier to service by dropping the whole engine/transmission/cradle from the bottom.

Service is definitely considered during the design and architecture phase of the engine and vehicle but the reality of the situation is that the powertrains are getting more and more complex and the packaging is tighter and tighter....there is really no way to escape this except to revert back to the more simple, large and inefficient vehicles of the past.

The fact that there is a "cut for service" nomenclature on the HVAC case is an indication that the service WAS considered ahead of time. It was known to be a "tight spot" and the solution was the HVAC cut.

In hind sight, you can loosen and remove the dog bone style torque struts on the powertrain and rock the engine forward for additional access to the blower motor fairly easily in your garage. There is no load on the torque struts with the car sitting in park on a level surface and the leverage of a 2x4 on one side of the engine will rock it several inches once the dog bones are disconnected....

While some things are harder to service keep in mind that the engine requires very little service for most all of it's life. Things like the roller chain timing drive provides a permanent, lifetime cam timing drive (instead of a belt) that never needs service. Hydraulic tensioners on the chains and tappets also negate the need for service.....

Stoneage_Caddy
03-09-05, 01:27 PM
I had a 1966 El Camino that the factory (Helms) service manual said that you used a 2x4 to pry the fender inner panel out of the way to change the blower motor. 1954 Mercuries were put on the market with no way to get the oil filter off unless the whole car was raised on a lift, the steering wheel cranked to one extreme, and then one wheel was manipulated with a floor jack. On a Chevy Monza you had to loosen the motor mounts and raise the engine to get some of the spark plugs past the steering gearbox. After the mounts got old you could pry the engine high enough with the 2x4 you had left over from the El Camino to access the plugs.

wasnt it the late 60s 427 cube mustangs had to have the engine removed to change the plugs according to the factory manual ?

not fun considering this was before the 100,000 mile plug .......let alone the 40,000 mile plug ....

blb
03-09-05, 01:52 PM
Given enough time and miles something is going to start to weaken in any engine. A Lexus engine will start to loose the timing belt at 100K or so, guaranteed. A Northstar might need a head gasket at that miles..... take your pick. I see it as an area for constant monitoring and improvement if the joint can be made more robust but not something that is epidemic or a low mileage failure.



You've got to be joking! You're comparing a scheduled maintenance item such as a timing belt job (under $1000) on a Lexus, to dropping the entire engine/trans/front suspension assembly, removing the heads, timeserting the block, replacing the headgaskets and reassembling, for $4500 or more? You can't be serious. No wonder GM is in trouble. Seriously, the GM Management and Senior Engineers really should have their new company cars revoked and be given 5 to 10 year old cars, they are responsible for maintaining, to drive. Then, they might understand first hand why the resale on these units is so poor.

dkozloski
03-09-05, 02:04 PM
Many years ago I worked with a man who had been a welder in Chevy's special engine plant in Flint. He said that if you had a Chevy car, you could arrange to take your car around to the back of the plant and if the workers could make it fit, they would exchange a new motor for the one in your car. Your old motor was torn down to try to spot in-service failures. FWIW, his job was repairing bad castings and forgings on a repair line that was parallel to the engine assembly line in order to lower the scrap rate.

BeelzeBob
03-09-05, 02:05 PM
You need to read my post a little more carefully. I said that a Lexus WILL require a timing belt replacement (a $1500 job the last time I checked a few years ago)....all of them will REQUIRE that. A Northstar MIGHT need a head gasket. Heavy on the "might" need a head gasket.

The post meant to imply that all engines have some point in their life that they need some work. The comparison was not of the two jobs but the fact that one is absolutely necessary and can run into thousands of dollars if not done and that the other may happen on some cars but not all of them by any stretch of the imagination.

BeelzeBob
03-09-05, 02:43 PM
It is kind of ironic that the Northstar is becoming it's own worst enemy in a way.....it is still running perfect with well over 100K on it in most all cases. Occasionally one of them might need some work on it. Might be a head gasket or might be an oil leak.....so.....since the engine and car seems to be pretty reliably getting out to those high mileages the chances get greater and greater some work will need to be done since more and more of the cars are living so long. Then people act like it is a new car having this problem. The simple fact that must be recognized is that the Northstar engine and the 4T80e transmission is reliably getting to WELL over 100-150K in all cases. That is a feat in itself that was not always the case even 15 years ago. Most all of the cars discussed regarding this are 8 to 10 to 12 years old....not something that the factory is still "studying"...... they are ancient history. Again, 15 or 20 years ago you would not have been expecting a 10 year old car (at that time) to be running without incident at 100K or better. The engines have proven over and over to be perfect inside with 100K, 150K, 200K on them. Little or no cylinder wall wear, no timing drive wear, no head work necessary, etc.. they last far better than anything from the past and are repairable if necessary. Just seems like the only thing that happens to them ends up being the head gasket or oil leaks and every one obcesses over that since there isn't much else to talk about....LOL. That is good in a way. Even people that have never had a head gasket problem weigh in on the subject as if it is immenient on every Northstar engine out there. Face it. It doesn't happen to that many of them and when it does it happens way way into the cars useful life. That is just part of the deal with used cars and high miles.

I always find it a bit hard to understand and accept when poeple post on this forum that they just bought a Northstar car with "ONLY" 100,000 miles on it. Somehow, until I started frequenting this forum the words "only" and "100,000 miles" were mutually exclusive terms. I have seen this quoted many times now and it always amazes me. Instead of dwelling on the fact that the cars are in great shape, no rust, still runs like a raped ape, etc...everyone starts badmouthing the engine and the design for an occasional head gasket failure at high miles.

I know it would be great if the engine ran forever with no problems. Can someone tell me what they think the "useful" life of a car and engine ought to be..?? To read this thread, 100k is just getting broken in and having to touch the engine at 150K is a disgrace to Cadillac. Personally, I think that a LOT of the useful life of an engine and a car is used up by 100K and at those miles it becomes a very used car and expenditures to keep it running are expected. Maybe I am wrong and maybe this is what is wrong with GM. But I find it hard to bad mouth any product that offers this level of service for 10 years and/or 100K with little or no problems and with little or no maintenance.

It would also be nice to hear others weigh in that have never had a gasketing problem on their Northstar to see what the ratio of repairs really is. Keep in mind that there are millions of them on the road and some are getting to be 13 years old.... As the absolute numbers increase on the road and the average age increases repairs are going to become more and more common with anything. So, counting the number of repairs a particular dealer does is as about as representative as thinking that this forum represents a scientific survey.

Besides, if you guys didn't have me to argue with, what would you do all day...????....sit around and complain to each other..... LOL LOL LOL

Maxoom
03-09-05, 02:56 PM
Hi guys. Great forum. Let me jump in here ...

Bbob, I sense you're the real deal - a factory engineer who's been part of the Northstar program from the beginning. Thanks for taking time to share your knowledge and experience. Glad you're willing and able to do so.

Cadillac has apparently decided that the Northstar head gasket failure rate is tolerable. There's nothing to argue about here. There's no right or wrong failure rate. You can disagree with Cadillac's judgement, but you can't prove them wrong. Naturally, you'll exercise your own judgement next time you buy a car.

My question is this: why are the threads in the block almost always damaged when the head bolts are removed? A blown head gasket is bad enough, but why do I have to damage the block and then repair it in the replacement process?

dkozloski
03-09-05, 03:28 PM
The standards in the financial world for many years have been that a car older than five years has no value. As loan collateral a five year old car is right there with five year old Sam's Club furniture. A business vehicle at this point has been depreciated to zero. You cancel the collision insurance and drive it until the wheels fall off. It's apparent that cars are now lasting longer to where repairs that would be a waste of time and money just a few years ago are becoming commonplace. Unfortunately there is no way to recover the expense other than driving the car until it finally falls apart. 7 to 10 year old Caddies hit the used car market and are still fine looking cars but the goody has been sucked out of them by the original owners who scheduled them gone at the end of five years and maintained them accordingly. Instead of going to the crusher at 7 to 10 years like a lesser car, now it is a still shiny car sitting in the driveway with a pool of fluids under it and an unhappy owner standing along side it with a repair estimate for a car that used to be worth $50,000 and the repair still costs the same but it has a depreciated value of zero. About the only thing that remotely apporaches a car for being a bad investment is a high maintenance trophy wife

BeelzeBob
03-09-05, 03:38 PM
Hi guys. Great forum. Let me jump in here ...

Bbob, I sense you're the real deal - a factory engineer who's been part of the Northstar program from the beginning. Thanks for taking time to share your knowledge and experience. Glad you're willing and able to do so.

Cadillac has apparently decided that the Northstar head gasket failure rate is tolerable. There's nothing to argue about here. There's no right or wrong failure rate. You can disagree with Cadillac's judgement, but you can't prove them wrong. Naturally, you'll exercise your own judgement next time you buy a car.

My question is this: why are the threads in the block almost always damaged when the head bolts are removed? A blown head gasket is bad enough, but why do I have to damage the block and then repair it in the replacement process?


I think it is a combination of lots of load cycles and wear and tear on the threads in the block from thermal and mechanical fatigue combined with the effects of having the steel bolts in aluminum threads for 10 or 12 years and then suddenly removing them. There is always some galvanic activity (that has been discussed to great length) that does tend to lock or bond the steel threads to the aluminum threads given enough time and heat and stress.... When the bolts are then removed, the aluminum threads are damaged to some extent. This appears to be much worse given 7 or 8 or 12 years of assembly time than it was/is seen in development where the bolts might only be in the holes for days or weeks or months.... The loads were the same and the thermal cycles are the same on accelerated tests as well as the cyclic mechanical loads on endurance testing and the aluminum threads hold up fine and dissassemble fine. Having worked on aluminum motorcycle engines for years I guess I just accept the fact that a bolt in aluminum that is undisturbed for 5 or 10 years "sticks" to some extent. The same with the Northstar head bolts, just the effect seems to damage the female threads enough that they later fail. I am just guessing and giving my own honest opinion, here. Some of this was anticipated and design steps to minimize the effect were taken by the phos and oil coating on the head bolts combined with the loctite patches to seal the threads from air as well as putting each head bolt in it's own, sealed , dry cavity to minimize any galvanic action of a corrosive solution settling around the bolts. I don't think the threads are damaged from corrosion as assembled during their life, but that the threads are damaged from the effect of the dissassembly after long time. In other words, the head gasket starts to weaken for one reason or another (hastened in the 93/94/95 years by the lack of cooling system maintenance in many cases) and then the bolt threads in the block are collateral damage when the dissassembly takes place. When the mechanic removes the head bolts and the aluminum threads are stuck into the bolt threads he assumes that the bolt was "stripped" before dissassembly. In fact, the bolt was fine and the threads were ripped out when the bolt was removed in most cases.

The fact that highly stressed aluminum threads fail to some extent after a period of many years and over 100K was also anticipated and that is why the timesert repair was developed and validated early in the Northstar engine's development schedule....long before the engine ever went into production. I remember drilling out the threads in brand new Northstar blocks to install timeserts so as to test the joint with the timeserts in place on the accelerated thermal and mechanical fatigue testing. It is just another aspect of anticipated service. The thread issue was anticipated, it was addressed with an appropriate service procedure , the parts and kits were developed and established and provided to the field along with the information in the service manual.

Imagine my frustration , knowing that the timesert information was published in the orginal service manual for the 1993 Allante, to find out on this forum several years ago that NO ONE HAD HEARD OF TIMESERTS...!!!! This is a pretty basic repair item that no one knew about until I mentioned it. Now it is all people want to talk about...but two years or so ago no one even had heard of timeserts. Every engine in the world (even the Briggs and Stratton on your lawn mower) has special tools required to work on it. Same with the timesert repair kit. Why does no one know about them or bother to read the service manual...???

Much is made over having to timesert the block but I cannot really understand that. It is a relatively easy repair that is very very effective, completely thought out and tested, readily available and actually quite quick to do. I timeserted a Northstar block several weeks ago myself and it took less than 2 hours of casual labor to do the timeserting of all 20 holes (several of which had been done previously with helicoils that failed.... and took extra time to pick out) and I am no expert nor speed demon. Why dealerships and garages that specialize in mechanical repair insist on making this such a big deal is beyond me. In a way it is no different from having to use new head bolts due to the preapplied loctite patches applied to the bolts and the load that the bolts see. Having to use new bolts seems acceptable but the timeserts do not....???.... To me, they are one and the same in a way.

I think (know...) also that many Northstar head bolt threads are damaged during reassembly of the engine after a repair due to not cleaning out the holes carefully, using lubes on the threads of the bolts as is NOT specified, cleaning the threaded holes in the block out with a cutting tap (quickest way in the world to ruin perfectly good threads) and when the bolt hole strips then it is , of course, not the tech's fault that ran the cutting tap thru the hole. Even a nick on a head bolt thread that starts to remove or gall material during installation can cause the hole to fail as the galling material will remove sufficient material from the threads to weaken them.


The one item that is always hard to predict in any product development is "father time". A manufacturer can speed up thermal cycles and run the engine full throttle for hundreds of hours straight to speed up load cycles but you cannot hurry time. I suspect the aspect of time that the bolts are installed into the block is the biggest culprit, here, causing the head bolts to frequently damage the threads in the block. Just my opinion based on what I have observed, though.


Funny thing is that, of all the motorcycle engines that I have helicoiled and timeserted threaded holes in I never actually thought along the lines of it being the manufacturer's fault.....hmmmm.......better get with the program along those lines!! I just figured that it was a steel bolt in an aluminum hole that was assembled for too long before I tried to take it apart. Ever try to get those damn philips headed screws out of a motorcycle engine case. You MUST use an impact driver to remove them....or a sharp chiesel to cut the heads off.....LOL At least the Northstar head bolts will come out....LOL LOL

BeelzeBob
03-09-05, 03:42 PM
The standards in the financial world for many years have been that a car older than five years has no value. As loan collateral a five year old car is right there with five year old Sam's Club furniture. A business vehicle at this point has been depreciated to zero. You cancel the collision insurance and drive it until the wheels fall off. It's apparent that cars are now lasting longer to where repairs that would be a waste of time and money just a few years ago are becoming commonplace. Unfortunately there is no way to recover the expense other than driving the car until it finally falls apart. 7 to 10 year old Caddies hit the used car market and are still fine looking cars but the goody has been sucked out of them by the original owners who scheduled them gone at the end of five years and maintained them accordingly. Instead of going to the crusher at 7 to 10 years like a lesser car, now it is a still shiny car sitting in the driveway with a pool of fluids under it and an unhappy owner standing along side it with a repair estimate for a car that used to be worth $50,000 and the repair still costs the same but it has a depreciated value of zero. About the only thing that remotely apporaches a car for being a bad investment is a high maintenance trophy wife



This is the similar situation as in Japan....cars there have a useful life of 5 years or so. After that the requirements to "maintain" them to the government standards exceeds the car's worth and most of them are scrapped..... Look at the robust trade in import engines from Japan. The car is written off in Japan, the scrapper cuts the front clip off and ships it to the US and the import scene snaps them up as 25k to 30K mile engines and transmissions are common from those cars. This is a fact of life in their market and culture.

1996deVille
03-09-05, 03:46 PM
Just to be clear... my Northstar is still running great at 114K! I believe the design is excellent - any mileage over 100K to my way of thinking is a bonus.

As cars become more complex so does maintence... it has to be tough to go through all the body/engine changes and keep general maintence in mind when engineering the product. You know how it goes... when you're used to being able to step inside the engine compartment of a '68 GMC pickup you want the same ease on the Northstar... sorry, can't have it both ways I suppose.

Anyway, good discussion! Make it a good day!!!

BeelzeBob
03-09-05, 03:52 PM
So.....gtm2u....has your head gaskets shown signs of failure...???....how many miles on your Northstar..???....and/or are you just preparing for the "inevitable" looking at studs....???? Just curious. When the day comes that you might need to do the repair, rest assured that the timesert repair, if done reasonably correctly, will outlast anthing else in the car...!!!

Loose screw
03-09-05, 04:11 PM
I saw some data that the Mazda RX-7 rotary motor went from being the worst engine on the market to the most reliable engine ever put in a car. Before they were discontinued only 0.1% ( 1 in 1000) of all owners reported engine trouble of any kind, for any reason, including running out of gas. The average milage where the trouble was reported was 168,000 miles. If I remember right CU is the source for this info. FWIW, I have seen several references that state that the europeans found that under certain conditions the DexCool type anti-corrosion package can attack the materials in modern head gaskets. I think the Swedes have done some work in this area.

The Mazda Rotary Engine was discontinued for a year or so and then re-introduced with major improvement both in performance and durability. http://www.mazdarx8.co.uk/rotary/rotarydetail.asp?documentid=1277 Many of the improvents involved many changes of materials used, gone are the days of using the materials and methods that were the high standard in industry, that wouldn't be near good enough to eliminate all the problems and meet all the goals. The old style rotary had great improvements and results but the new engine with the new very stable materials it vitually eliminated all the weak or trouble spots and turned weakness into strengths. It's an impressive accomplishment by Mazda (now 60% owned by Ford I heard) to stick with it, to face the many early problems squarely and insist on solving them completely and then insisting on making it even better, and then much better than that. It raised the cost of manufacturing the engine - but what a result.

dkozloski
03-09-05, 04:13 PM
Corrosion and thread damage due to age is very uncommon in air cooled aircraft engines. Of course all fasteners are cadmium plated and coolant is not present. The same cannot be said for aircraft structures. I have seen heavy aluminum forgings that were improperly heat treated that had the structural integrity of wet cardboard and could be picked apart with a pocket knife. I have seen entire aircraft that were completely corroded by an improperly applied paint job in less than a years time through the process of exfoliation. One of the big surprises is the reaction between some stainless steels and aluminum. The aluminum sacrifices to the stainless and looks like it came out of Mammoth Cave. When a steel to aluminum junction corrodes the white powder that forms occupies a greater volume than the original material and the subsequant expansion can cause trouble of its own. Aluminum corrosion can take several forms. The one we are all used to seeing is the white powder that forms on the surface of bare aluminum, particularly with chemical contamtination that is basic in nature. Intergranular corrosion takes place below the surface and is usually the result of bad heat treatment. The material deteriorates along the grain boundaries. This turns the aluminum to gray dust or crumbly material when dry and wet cardboard when dampened. I used to teach this stuff at an aircraft and powerplant mechanics school. The aircraft industry still gets hit with billion dollar corrosion surprises. Remember the plane in Hawaii that the roof came off? Loose head bolts in comparison are pretty silly.

blb
03-09-05, 07:29 PM
Just to be clear... my Northstar is still running great at 114K! I believe the design is excellent - any mileage over 100K to my way of thinking is a bonus.


This quote would not surprise me at all if we were having this discussion in the 1960's or 1970's. But since unleaded fuel has been used exclusively and since modern fuel injection systems are used exclusively, if an engine can't go AT LEAST 150,000 if not 250,000 miles without pulling the heads or the oil pan, something is seriously wrong.

The fact that it is a surprise or particularly noteworthy that someone's Northstar made it 100,000 miles, in itself is a testament to the fact of how low the expectations are for these vehicles, especially given the fact that these cars original MSRPs were $40,000 to $50,000.

Heck, even Hyundai warrants their powertrains to 100,000 miles. It might just put GM out of business if they matched Hyundai's warranty on the Northstar. Truly sad........

1996deVille
03-09-05, 08:39 PM
DK,

Very true about aluminum break down within joint structures... I spent most of my time in R&D in the Model Shop at Boeing - when I was sent out to different jobs the most interesting was always AOG (Airplane On Ground). Those folks are amazing in what they can do with very little time (like rebuild a landing gear assembly while being shelled in a war zone) and with simple repair equipment.

The joints we fly around on in our schedules are in most cases in much worse condition than the Northstar head to block attachment.

I wonder how much time will pass before we find composit material for engine blocks and heads...?

BeelzeBob
03-09-05, 08:42 PM
This quote would not surprise me at all if we were having this discussion in the 1960's or 1970's. But since unleaded fuel has been used exclusively and since modern fuel injection systems are used exclusively, if an engine can't go AT LEAST 150,000 if not 250,000 miles without pulling the heads or the oil pan, something is seriously wrong.

The fact that it is a surprise or particularly noteworthy that someone's Northstar made it 100,000 miles, in itself is a testament to the fact of how low the expectations are for these vehicles, especially given the fact that these cars original MSRPs were $40,000 to $50,000.

Heck, even Hyundai warrants their powertrains to 100,000 miles. It might just put GM out of business if they matched Hyundai's warranty on the Northstar. Truly sad........


Do you realize that your comments are somewhat like 20/20 hindsight...??? You are talking about a 10 year old vehicle (in general) as if it were new today. Think of the expectations back in 1990 or earlier when the engine was developed and 1992 when it was first put into the market. At that time typical vehicles were still reaching the end of their life at 100K/10 years. Since that time (15 years ago in general) the expectations have certainly changed. That is why things like the head gasket joint and seals and fasteners have been constantly upgraded as ongoing improvement. That is called progress and change. You cannot go back and judge a 1993 Northstar based on what the market expectations are TODAY. That is nothing but hindsight.

The was considerable thought put into the longevity of the Northstar even back then. The fact that most of them can easily go 100K miles with no tuneup or other maintenance other than oil and filter changes is a testament to that direction. So the expectations TODAY are that the engine go 200K...??? That doesn't change what was produced 15 years ago.

1996deVille
03-09-05, 08:44 PM
BLB,


I hear you... I bought my Cad with 68K. I did the best I could to check it over before purchase. But, you know how that goes - sigh...

I've been able to run my new cars well past 100K, where I controled the maintence schedule. But, I'm not sure how well my Cad was maintained before I took the car.

Just my 2 cents, your mileage may vary...

BeelzeBob
03-09-05, 08:57 PM
Not to change the subject....but..... If you have been reading about the new BMW 3 series it has a rather special engine block that is really pressing technology in the interest of mass savings. The main part of the block that handles the coolant and mounts the cylinder liner area and main caps is aluminum. The aluminum "core" is captured inside a magnesium casting that comprises what would be viewed as the the exterior of the block. The coolant is inside the aluminum part of the block and does not touch the magnesium. All the exterior pieces, brackets, mounts, etc... mount to the mag casting. The large part of the casting being made of mag saves about 24 pounds from what their press literature indicates. It will be interesting how that structure handles corrosion and galvanic action, etc... over time...like over the next 15 years.

dkozloski
03-09-05, 09:35 PM
Dow chemical company was really big in the magnesium world right after WWII. They promoted the use of magnesium for just about everything. As part of this promotion effort they developed a multitude of chemical treatments of magnesium alloy materials called Dowtreat #'s 1.2.3...etc. Aircraft manufacturers trying to be on the leading edge of technology got sucked into this program and payed the price for years to come. There are a multitude of service bulletins, Airworthiness Directives and service advisories to be found on magnesium forgings and castings. Beechcraft in particular used a lot of magnesium for control surfaces that have about all had to be replaced. It is interesting to note that the outboard motor manufacturers have embraced a line of alloys of aluminum and magnesium called "white metals" that seem to do well in salt water at resisting corrosion. The down side is that they are very difficult to weld after they have been damaged using any technique. Magnesium, even when alloyed and in pretty heavy castings will burn to beat hell and is hard to extinguish. I stood alongside an airplane crash and watched as the crash crews ran around trying to find something to extinguish the burning oil sump and intake on an engine and the wheel castings. I finally got tired of the show and went and got a shovel and shoveled some dirt on it and put it out for them.

1996deVille
03-09-05, 09:54 PM
DK,

You beat me to it - I can just see the day a shop guy lights up the welder to do a quick fix... yikes, it'll burn the whole dealership down!!!

What a waste of time for 24 pounds.

dkozloski
03-09-05, 09:56 PM
Terrier and Tartar Surface to Air Missiles made by General Dynamics for the Navy had magnesium as the basic structure. The Navy being the Navy would send some of these missiles back to the depot from the fleet broken in half somehow which gave me the opportunity to play around with some of the damaged pieces. These alloys were tough beyond belief. Some pretty thin stuff would withstand an assault from a pretty big hammer without bending. I was really impressed.
If a missile was scratched during assembly and testing it required a five coat corrosion proofing and finishing process to repair it. Believe me, every scratch was repaired. Every buggered screw head and damaged nut or bolt was replaced. There was a separate line just for this type of repair.

Ranger
03-09-05, 10:58 PM
This has been a very interesting post and i have learned a few things. There are some very good points on both sides. I have always considered a head gasket as a major repair and not one that I ever looked forward to. I guess the thing that botheres me the most (if it ever happens) is that I can no longer do it myself. A car that has depreciated in value and is otherwise in great shape used to be salvageable with some time and a few hundred bucks by a reasonable competent DIY'er. Sadly, that seem not to be the case. If it was doable with the engine in the car, then I could accept it a little more. Lets face it, not many of us have the capability to drop the drive train in our garage. I also understand the restraints given the engine size and space to put it in. I guess that's just the price of progress. I can't wait for rear wheel drive to become the norm again and have an engine longitudally mounted, the way God intended :)

Stoneage_Caddy
03-09-05, 11:11 PM
This has been a very interesting post and i have learned a few things. There are some very good points on both sides. I have always considered a head gasket as a major repair and not one that I ever looked forward to. I guess the thing that botheres me the most (if it ever happens) is that I can no longer do it myself. A car that has depreciated in value and is otherwise in great shape used to be salvageable with some time and a few hundred bucks by a reasonable competent DIY'er. Sadly, that seem not to be the case. If it was doable with the engine in the car, then I could accept it a little more. Lets face it, not many of us have the capability to drop the drive train in our garage. I also understand the restraints given the engine size and space to put it in. I guess that's just the price of progress. I can't wait for rear wheel drive to become the norm again and have an engine longitudally mounted, the way God intended :)

sadly rear wheel drive isnt much beatter anymore , even as far back as the 89-97 T birds are aweful to get the plugs out of let alone R&R a head...and forget it with a 93+ F body (i havent done one of these but it doesnt look pretty)

alltho the 2.7l v6 Magnum looked pretty nice to work on , but theres tons of room in that version becuse its availble with the 5.7 hemi v8

i still think the 84-96 Vette had to be one of the easiest modern cars to get at the engine on....

haymaker
03-09-05, 11:15 PM
Bbob my hats off to ya, you are the best I have ever seen or at least heard of, the time-sert installation champ! Here for quite a while now I thought onebaddude was the time-sert installation winner but you topped him unless you are onebaddude. Letís see, how about we run some numbers on your amazing feat. In post #82 of this thread you stated you installed 20 time-serts and removed some old helicoils that happened to be in the way in less than 2 hours of course you accomplished this task as you were just loafing around the shop or garage (I think you used the term ďcasual laborĒ). 2 hours=120 minutes, all thatís right you said less than 2 hours, letís see 115, 110 minutes, probably 110 minutes. Letís see removing those tricky old helicoils that are several inches down below the deck surface in that blind ĹĒ+ diameter bolt hole. I donít know how many helicoils you removed, say 3 for a nice odd number now for the removal time for each, engineers are very sharp so no way it would take you more than 10 minutes to remove all 3 helicoils. How many minutes we working with now letís see 100 minutes give or take. Give me a minute here Iím a little slow. 100 minutes divided by 20 time-serts= 5 minutes per insert install. Wait a minute here if you had those 3 helicoils in the block then you needed to use the big-sert install kit at least on the helicoils bolt holes which means you needed to drill (ream) the entire length of the bolt hole. I guess you could have implemented the onebaddude method and cast the drill fixture plate into the trash and just drilled, tapped and installed the inserts haphazardly. I donít know though installing the big-serts without a guide plate (drill fixture plate) in MHO would be a bit risky to keep centered and aligned but I am no engineer. Letís step back and see what you have done. You have an installation average of 5 minutes per big-sert or mixed big-sert, standard time-sert. You now have the record and to think we non-engineer garage, driveway types have our time-sert installation averages up around 20 minutes per hole. Leave it up to some engineer to show us all how itís done. Sure wish you had taken a video of your time-sert job bet we all could have learned a thing or two.

For those who have never installed a time-sert go to the time-sert web site http://www.timesert.com/misc.html and read the time-sert installation instructions for the Northstar Second repair to help you get a feel for just how fast bbob installed his time-serts

What say all my fellow time-sert installers does bbob get the time-sert trophy?
BTW should I have included any coffee breaks or catnaps in the calculation? LOL..

dkozloski
03-09-05, 11:34 PM
Stoneage Caddy, for access you can't beat one of those new GM/Isuzu Chassis cabs. You just work the lever behind the cab and the whole works tips forward exposing the entire engine and drivetrain. All the service points are on the back of the cab.

Stoneage_Caddy
03-09-05, 11:39 PM
Bbob my hats off to ya, you are the best I have ever seen or at least heard of, the time-sert installation champ! Here for quite a while now I thought onebaddude was the time-sert installation winner but you topped him unless you are onebaddude. Letís see, how about we run some numbers on your amazing feat. In post #82 of this thread you stated you installed 20 time-serts and removed some old helicoils that happened to be in the way in less than 2 hours of course you accomplished this task as you were just loafing around the shop or garage (I think you used the term ďcasual laborĒ). 2 hours=120 minutes, all thatís right you said less than 2 hours, letís see 115, 110 minutes, probably 110 minutes. Letís see removing those tricky old helicoils that are several inches down below the deck surface in that blind ĹĒ+ diameter bolt hole. I donít know how many helicoils you removed, say 3 for a nice odd number now for the removal time for each, engineers are very sharp so no way it would take you more than 10 minutes to remove all 3 helicoils. How many minutes we working with now letís see 100 minutes give or take. Give me a minute here Iím a little slow. 100 minutes divided by 20 time-serts= 5 minutes per insert install. Wait a minute here if you had those 3 helicoils in the block then you needed to use the big-sert install kit at least on the helicoils bolt holes which means you needed to drill (ream) the entire length of the bolt hole. I guess you could have implemented the onebaddude method and cast the drill fixture plate into the trash and just drilled, tapped and installed the inserts haphazardly. I donít know though installing the big-serts without a guide plate (drill fixture plate) in MHO would be a bit risky to keep centered and aligned but I am no engineer. Letís step back and see what you have done. You have an installation average of 5 minutes per big-sert or mixed big-sert, standard time-sert. You now have the record and to think we non-engineer garage, driveway types have our time-sert installation averages up around 20 minutes per hole. Leave it up to some engineer to show us all how itís done. Sure wish you had taken a video of your time-sert job bet we all could have learned a thing or two.

For those who have never installed a time-sert go to the time-sert web site http://www.timesert.com/misc.html and read the time-sert installation instructions for the Northstar Second repair to help you get a feel for just how fast bbob installed his time-serts

What say all my fellow time-sert installers does bbob get the time-sert trophy?
BTW should I have included any coffee breaks or catnaps in the calculation? LOL..

ok i dont get it ?
why does everyone line up to get a shot in on bob , whad he do to you ?

Do you all have a beatter way ? How come GM didnt think of it ? its not like Bob did it all by himself , im sure a "team" desgined the engine ? do you all think they may have forgotten something with all the resouces and R&D behind the engine? what was it ?

Remeber the real GM lemon engine ? the 2.3 vega , gm dumped tons of money in that , only ran it for 7 years and tons of revisions before pulling the plug , they knew it was bad and got rid of it. the northstar is almost 15 years old , if this engine was junk GM would have pulled the plug years ago.

I do agree you sevice techs are seeing alot of northstars being brought in with head gaskets , and we see alot of them here ....But does anyone bring in a perfectly healthy northstar to cadillac for a headgasket or other job that requires the high tenure mechanic? How many folks joined us with a perfectly healthy 100% northstar car ?

Come on down here to tampa florida if you think the northstar is a junk engine ...ill show you that what you have seen witht he hood up is a drop in the bucket , all i see everyday is northstar cars with Q tip people driving them. Knowing that i know they dont see WOT runs to prevent oil consumption or anything , and you know how old men are about things being wrong with there "automobile"...

Im sorry i just dont see whats so bad about these engines , becuase every day on my way to work the left middle and right lanes are clogged with snowbirds in 12 year old cadillacs powered by northstars....

Its not like real junk engines , i dont see GEO metros hardly anymore , i barely see the SHOC v6 mitsu powered chryslers , and a turbo chrysler is a rare thing .....

And 4cyl Plymoth Breeze Crrus Stratus cars are getting might thin after the engines that blow apart insatntly at highway speeds

sorry for the rant but i just dont understand the point here ....ive seen some real junk in my life ...but the northstar just doesnt fit that bill for me

perhaps you all would be kind enough to explain it to this firetruck mechanic ?

Stoneage_Caddy
03-09-05, 11:43 PM
Stoneage Caddy, for access you can't beat one of those new GM/Isuzu Chassis cabs. You just work the lever behind the cab and the whole works tips forward exposing the entire engine and drivetrain. All the service points are on the back of the cab.


Oh yah those are NIIIIICE had a couple in the eielson fleet i think....even beatter ,We had the cabover style firetrucks (pretty much all depts do), man those were nice to work on ....flip the lock and press a swtich and the cab raised off automaticly to its locks ....that was untill Kovatch relesed a recall on the fire engines hing assembly as they "could fatigue crack and fail" ..i was rather nervous till replacemnt parts arrived

BeelzeBob
03-10-05, 12:53 AM
Bbob my hats off to ya, you are the best I have ever seen or at least heard of, the time-sert installation champ! Here for quite a while now I thought onebaddude was the time-sert installation winner but you topped him unless you are onebaddude. Letís see, how about we run some numbers on your amazing feat. In post #82 of this thread you stated you installed 20 time-serts and removed some old helicoils that happened to be in the way in less than 2 hours of course you accomplished this task as you were just loafing around the shop or garage (I think you used the term ďcasual laborĒ). 2 hours=120 minutes, all thatís right you said less than 2 hours, letís see 115, 110 minutes, probably 110 minutes. Letís see removing those tricky old helicoils that are several inches down below the deck surface in that blind ĹĒ+ diameter bolt hole. I donít know how many helicoils you removed, say 3 for a nice odd number now for the removal time for each, engineers are very sharp so no way it would take you more than 10 minutes to remove all 3 helicoils. How many minutes we working with now letís see 100 minutes give or take. Give me a minute here Iím a little slow. 100 minutes divided by 20 time-serts= 5 minutes per insert install. Wait a minute here if you had those 3 helicoils in the block then you needed to use the big-sert install kit at least on the helicoils bolt holes which means you needed to drill (ream) the entire length of the bolt hole. I guess you could have implemented the onebaddude method and cast the drill fixture plate into the trash and just drilled, tapped and installed the inserts haphazardly. I donít know though installing the big-serts without a guide plate (drill fixture plate) in MHO would be a bit risky to keep centered and aligned but I am no engineer. Letís step back and see what you have done. You have an installation average of 5 minutes per big-sert or mixed big-sert, standard time-sert. You now have the record and to think we non-engineer garage, driveway types have our time-sert installation averages up around 20 minutes per hole. Leave it up to some engineer to show us all how itís done. Sure wish you had taken a video of your time-sert job bet we all could have learned a thing or two.

For those who have never installed a time-sert go to the time-sert web site http://www.timesert.com/misc.html and read the time-sert installation instructions for the Northstar Second repair to help you get a feel for just how fast bbob installed his time-serts

What say all my fellow time-sert installers does bbob get the time-sert trophy?
BTW should I have included any coffee breaks or catnaps in the calculation? LOL..



The engine was out of the car and on an engine stand with the heads off. All I did was help the individual do the timeserts on the bare short block sitting on the stand. Didn't even clean up the chips and mess afterwards. The helicoils came out rather easily if you immediately get medival with them and rip them out with needle nosed pliers. I had to drive a large easy-out into one of them but that didn't take long either. Drilling all the holes goes quick when you drill them all at once. Put the tap in a drill motor and things go much quicker. If you wrap a wad of tap around the step drill and the tap it makes a convenient stop against the deck so that the depth is controlled that way. Yes, I eye-balled all the drilling and tapping and did not use the alignment fixture. By the way, I didn't do all the steps on each timesert one at a time. I drilled all the holes first, then did all the tapping and then just screwed all the inserts in. All the holes were big-serted so there was no mix and matching of taps and drills. The drill for the bigserts that I used is called a dreamer...half drill half reamer so it does the oversize hole for the bigsert, reams the upper part of the hold and makes the step all at once. The install tool was in the drill motor, too. My friend who owned the motor was screwing in the inserts also, so I had some help. It is really not that hard to do if you have done it a few times...LOL LOL Maybe if you practice up we can have a contest....???

gtm2u
03-10-05, 01:44 AM
...
For those who have never installed a time-sert go to the time-sert web site http://www.timesert.com/misc.html and read the time-sert installation instructions for the Northstar Second repair to help you get a feel for just how fast
...


Intentional or not what really bothers me is someone who comes across as credible and then you start reading and noticing things which don't add up. What a shame that some cannot stay within the bounds of what they know without crossing the line and manufacturing information which is not supported by any known facts. I understand that sometimes things get cloudy and memory plays tricks on us. But when numbers start getting manipulated to suit proving an argument (legal context) it just casts doubt on all that is presented. Drawing from legal imagery nothing can please opposing council more than to catch someone in not being straight arrow, when that occurs council usually will impress upon the judge and jurry these transgressions.

I understand character flaws, I understand, memory mistakes, I understand to some degree the need to have an ego, but I don't understand why some are driven to such an extreme that they must bring harm to others when confronted. Reminds me of that famous saying about killing the messenger when they brought bad news. I have never felt the urge to be a combatant when someone is holding a 12 gauge to my head. I learned a long time ago when as a kid that I wasn't good at something less than honesty. I cannot imagine that my words would change anything any more than what should have been learned years before. It does however fall into the Rand study which indicated the new moral turpitude is not what it was 40 years ago. As you approach the doors to Hell there is an inscription above which translates: 'remove all hope ye who enter'. Once burned twice warry.

Cheers,
GTM2u

dkozloski
03-10-05, 02:32 AM
I appears to me that gtm2u is implying that Bbob is blowing smoke when he said he installed the timeserts in two hours. I think Bbob did a very credible job in explaining his procedures. Removing heli-coil inserts is very easy if you know how to do it especially if you don't have to worry about putting one back in the same hole. With a Heli-coil down in a hole you just use a big screwdriver to snag the top coil enought to back it out a half turn to where you can grab it with the needle nose or the duckbill pliers. Three minutes equals three heli-coils. An awl down the hole and forced behind the top coils will also let you grab it with pliers. It's the little ones that can give you fits. If you drill them all one after another freehand and let the drill follow the hole with a piece of tape for a depth gauge that is a piece of cake. A good sharp tap of the correct format for clearing aluminum chips is easily driven by a good variable speed drill especially if you have the proper cutting fluid. With the inserting tool you Just run the insert in until it stops on the shoulder. Again a piece of cake. Bbob, what the hell took you so long?

dkozloski
03-10-05, 02:51 AM
Something that has been a problem to me all my life is that I can do a machining or mechanical job with no trouble that seems to me to be straight forward and almost self-explanitory. I will explain to someone else what I did and give them a rundown on procedures and turn them loose. A half hour later I'll come back and they are in so much trouble that I can't believe it. I'm trying not to boast but as Dizzy Dean said "It ain't braggin' if you can do it.". There are some people that have a natural talent with machinery that can see things in their head and accomplish repairs that most other people can't do. If you have 10 mechanics working for you, you are lucky if you have two that can do eveything well. You will have two that you wish would just stay home. The rest are the troops and the plodders that can do the mundane day to day work. My guess is that Bbob is the kind of engineer that is worth 10 men because he can see in his minds eye what he wants to accomplish and knows how to get there. I'll also bet he gets frustrated with people that don't see things as clearly and easliy as he does. I think that gmt2u is suffering from a bad case of sour grapes.

gtm2u
03-10-05, 08:32 AM
...
that is worth 10 men because he can see in his minds eye what he wants to accomplish and knows how to get there. I'll also bet he gets frustrated with people that don't see things as clearly and easliy as he does. I think that gmt2u is suffering from a bad case of sour grapes.

You asked for some history, I gave it to you.

I have yet to learn anything in this thread that I haven't done dozens if not hundreds of times.

It's my turn to toss out some numbers which you can accept or ignore. There are some place between 20,000 and 30,000 cars I have worked on in my life. My engines have 2 second place wins at USRRC Daytona, my skills make me in the top 99%, I run fewer than .001% comebacks.

The statement was made that x task could be done in y min, when confronted with this accomplishment we learn that something so simple as cleaning wasn't included. He was dealing with a bare block and someone to help in some limited engagement. I've owned automatic reversing drill motor chucks because they were faster when presented with tasks such as this. When I taught I did time studies on my students and have a pretty good idea how long jobs take for they were published in flat-rate manuals.

As for the quip about sour grapes I don't have a clue what that's supposed to mean. I've not lambasted the car, I don't have oil leaks or consumption problems. I came here asking for information addressing the head bolt and torn threads issues. The most offensive comment was that the engineers either didn't know or were forced to accept lesser standards by those who's job it is to cut corners. Period. I made no personal attacks, didn't try to ridicule any person yet the knee jerk reaction was not to give straight answers but to make blanket statements which were totally unfounded. I'm not going to assign guru based on what I've read. It doesn't take rocket science to know what ever his roll was in the development it's not as significant as we are led to believe.

Before I knew this list existed I went to the source of those in charge of developing what was supposed to be a reliable repair. I went to the tool maker and discussed my findings. Neither were happy campers because something was compromised. I went to dealerships and talked with senior techs who were there before these were on the market. I find that incredible that they (Cadillac) don't have competent staff who knew how to fix the damn thing. Certainly no grease monkey who has to make a living fixing some of the crap these makers toss at us would know diddly squat. Nobody in their right mind would suggest using a Helicoil and yet that was the first bulletin ever issued to every dealer on this problem.

I wanted to know the properties of the aluminum, instead I get a lesson on cut threads as if I had my head up my backside since I was in high school. I wanted to know the tensile strength of the bolts so I could do my own calcs based on what I knew and not the approved engineering handbook they used. As I recall you brought him up to speed on what he should have known and you had the ability to grasp I also knew. Yet there was no mention that the 10 inboard casting bosses stick out like some sort of an afterthought and then blames the head gasket. I don't know if anyone remembers the Vega... maybe that's where they got the idea. Now there was a thing of beauty and joy forever. Oh it can't have electrolysis there is no water, nono don't need to copper coat them... gotta be the head gasket forget the periodic chart. Forget the head is expanding 7 times that of the bolts they used that can't tear threads.

You have obviously a wealth of knowledge and given me no reason to doubt your credibility, just wondering out loud when the fuzzy math and other things were being tossed out why nothing was said. I realize the relationship and respect is there and I would have thought you knew the difference. But when you know something is incorrect is it policy to say nothing? I've had to suffer watching co-workers pull some incredible ignorant stunts, I have no problem keeping up with even the misinformation and I've seen nothing to suggest that my mental abilities are any less acute. I've worked for Nobel Laureates, I've had my cause argued before the US Supreme Court and my perspicacity hasn't let me down yet.
.................

That aside, from an earlier post you mentioned a rocket casing was made from Mag but was harder than a whooers heart. I was wondering if it could have been titanium? I don't have a lot of experience with it but boy it sure rings some bells when I came upon some piece thinking it was aluminum and started to work. Haayyyy I know my drill is sharp but nothing is happening, smack it against the vise, doesn't sound like 6061T6, put it to a grind stone to eventually identify it. I needed a sleeve for an exposed hydraulic anchor winch I was building, the material just needed a couple of quick passes on the lathe, 2 hours later.

There was some mention of welding Mag, it's done in an innert gas environment that excludes any oxygen or water. And probably not prudent to try with a MIG or TIG hand unit because you can't flood enough gas at the weld to cool it off. But what do I know.

I really don't see much point in this discussion from my perspective. The subject suggested that there was something to be learned and maybe for those who have difficulty understanding basic mechanics it satisfied them. Fortunately my bread and butter doesn't depend on the nonsense I've encountered, it most certainly was counter productive and a waste of my time. Who knows, maybe it's more sinister; it's deliberate, discredit, attack, ridicule anyone that says there is a problem. Geepers, what a sucker I've been, played right into that shell game and didn't see it coming, typical Detroit.

GTM2u

1996deVille
03-10-05, 11:54 AM
GTM2U, Bbob, et al,

This seems to be related to the Northstar head gasket concern, so I don't think I've highjacked this thread...

Do you have any real world experience with BarsLeak? I have talked with a lot of folks lately (Cad as well) and the concensus seems to be that this is a last resort to stop leaks in the Northstar platform. I have used this product in rare cases and found that it leaves residue in low places - hey, there's a song in there somewhere!!!

Anyway... I found it sitting in the bottom of the radiator, sitting in heater cores, etc, etc... what's the deal with this stuff from the field?

Thanks in advance.

BeelzeBob
03-10-05, 12:24 PM
Geez.....sorry you guys got so caught up in how long it takes to do timeserts....

I just mentioned that the job I did went smoothly and quickly. No, I didn't have to pull the engine or do any of the bull work. Sorry if that was misrepresented in any way. The particular engine I am talking about is going into a street rod so it was apart and on the engine stand anyway. No, I didn't clean up afterwards...that would have taken some time, yes.

BTW....we did have shop air plumbed to the site which makes it easy and fast to blow the holes out each time. It takes longer to vacuum and to make sure chips don't go where they don't belong if the engine is partially assembled.

.....there were only two helicoils that had to be removed. They came out quite easily.

......I use "Tap-Ease" or "Tap-Magic" cutting solvent on the dreamer and the tap. Smells like trichlorothane...???...works like magic. Tap never loads up and threads cut perfectly clean and fast. I will probably develop brain cancer from breathing it but it works excellent....LOL



I find it kind of annoying when people imply that I make up things for convenience. I'll give you a hint....this was not the first time I had timeserted a Northstar block...and probably will not be the last. I know it is foreign to the "mechanics" out there to consider that an "engineer" might be able to get up out of his chair, walk away from his desk and pick up some tools and know how to use them. Guess what....from my experience I find that I can wrench with a LOT of the supposed mechanics out there. Glad I don't have to do it on a daily basis...but I can do it when necessary.

My whole point was not to establish a benchmark for timeserting a Northstar block but to illustrate the point that it is not THAT hard to do and doesn't take FOREVER like a lot of people make out.

gtm2u....there was no service bulletin stating to repair the Northstar headbolt holes with helicoils. Either you got bad info or are making up a convenient story to support your BS. The factory service manual for the 1993 Allante covers repairing the Northstar head bolt holes with the correct timesert kit. I have a hard copy of that service manual that was published in the spring of 1992 when the Northstar engine started production. You either talked to the wrong people or they gave you a line of BS to make you go away. The correct repair procedures were developed, tested, validated, documented, supplied to the field with adequate instruction and information and the hard tools were available for the start of production of the engine in 1992 calender year. I know this for a fact. Your info is wrong.

If no one in the dealer ship you walked into knew how to repair the engine then all I can say is that they obviously did not take the time to read the service manual published for that purpose. Obviously, neither did you....maybe that would be the first place to start your "investigation". Heaven forbid the thought, I know, that the manufacturer might have covered this already in the service documentation.....

gmt2u keeps wanting numbers and facts....same old story. Notice that I give him the "facts" on his theory that the head bolts are barely capable of holding the force of compression (proving him wrong in the process) and he just ignores it and keeps wanting "facts"...... The tensile strength of the bolt has absolutely nothing to do with the load generated during the tensioning process. I affects it yes, but knowing the tensile strength does not tell you what the loads are. I know the actual loads, not from a text book or handbook as implied, but thru actual measurements done on real engines in the real engine plant where the engines are built. They are also measured on dyno engines and all other critical lab, endurance and validation engines. If you don't believe this, fine, but the information is real.

I am still curious as to why gmt2u made the comment that the fastener industry does not use torque-angle "anymore" since they "turned their back on it"....???? Care to comment as to the source of that information. I know that the fastener industry embraces torque-angle as a much more accurate method of tensioning fasteners. I cannot understand how anyone could make the comment that it is not used anymore.

gmt2u mentions that he talked to the "tool maker"...I suppose this is to imply that he talked with timesert...and they "were not happy campers...???" Having worked personally with timesert and having met with them in development and in the Northstar engine plant on several occasions I had no feedback from them that they were "un happy campers..." They supply application specific inserts for the Northstar head bolt holes that were developed for that application and tested and validated to be capable of holding the head bolt loads. What more can be said.

The 10 inboard casting bosses stick out like a sore thumb.....LOL LOL....are you looking at the same block that I am..??? The inboard head bolt bosses are anchored into the lower casting structure of the block and kept divorced from the cylinder walls (particularily in the upper reaches of the bore where the rings travel) to minimize bore distortion from head bolt tension. The inboard and outboard bosses are integral to the deck rail of the engine block. Inboard ribbing and outboard ribbing of the block adds stiffness to the deck face wall...is that what you are referring to as "sticking out like a sore thumb..??"

The specifics of my involvement with the Northstar engine over the years will remain a mystery on this board....sorry , but that is the way it is. I can assure you, however, that I have worked on and around it since it was just a gleam in our chief designer's eye. I have worked in all stages of design, development, release and manufacturing of the engine....and still do today.

dkozloski
03-10-05, 12:37 PM
gmt2u, Terrier and Tartar missiles were indeed made from magnesium and not titanium, The alloy used was very springy and would just rebound when hit with a hammer. I would guess that it was stiffer than normalized 4130 steel. I have done much Tig welding of magnesium in the field. If you lose your gas envelope for an instant the weld is contaminated and the part is ruined. It's easy to spot though because you can see the black smudge and the white powder when it happens. I did a lot of TIG welding inside a small cardboard box with some handholds cut in the sides and a sheet of acrylic plastic over the top and flooded with argon. As I said, outboard motor manufacturers use alloys from the group called "white metals" that feature magnesium as the parent metal but alloyed with aluminum. What I didn't mention was it can also include zinc. At this point they start acting like pot metal and giving trouble from puddling and slumping issues. All that being said, I agree with a lot you have to say. I think there is something that can be done to improve the stud to block transition so that the aluminum does not go to hell from some, so far undetermined, mechanism and allow the engine to be disassembled without tearing the threads. In the aircraft engine overhaul racket we used a sealer on the gaskets, not to seal the gaskets but as a release agent to make the engine easier to disassemble at the next overhaul.
I have to differ with you on the design of the block casting in the area of the bolt anchors. The Northstar looks to be a rendition of an open deck Deutz diesel done in aluminum rather than cast iron. Also there appears to be no distortion of the bores when the bolts are tightened which is the over riding design issue in this area anyway. How about some specifics from you on what you would change to address some of the problems that are appearing in the field. For instance, I would use studs with rolled threads in place of the head bolts but I would put the heads on first and then run the studs in to the appropriate depth using a mild interferrence fit. Then I would use hardened and ground washers followed by high strength spline drive nuts. What do you think?

BeelzeBob
03-10-05, 12:40 PM
GTM2U, Bbob, et al,

This seems to be related to the Northstar head gasket concern, so I don't think I've highjacked this thread...

Do you have any real world experience with BarsLeak? I have talked with a lot of folks lately (Cad as well) and the concensus seems to be that this is a last resort to stop leaks in the Northstar platform. I have used this product in rare cases and found that it leaves residue in low places - hey, there's a song in there somewhere!!!

Anyway... I found it sitting in the bottom of the radiator, sitting in heater cores, etc, etc... what's the deal with this stuff from the field?

Thanks in advance.


Yes, I have LOTS of "real world" experience with the BarsLeaks products. I conducted extensive tests on the stuff back in the early 80's to confirm earlier testing that it works, that it does not clog things up and that it is effective against internal coolant intrusion in an engine.

If you have read any of my posts on this forum I have related a number of real world cases where the BarsLeak or GM Coolant Supplement was used in practical applications where it worked very very well.

Yes, it can cause some sediment, over time, in quiet flow areas of the cooling system. So what...the fact that the coolant flow was low or quiet at that area means that the area isn't going to be affected by the sediment. Most times when heater cores plug they plug from gelling coolant...then the gelling coolant traps the particles of sealer. So...the natural reaction is that it was the sealer that caused the problem. It isn't. If the heater core is plugged it is not because of the supplement...it was plugging anyway from gelling coolant and other particulates (like rust from the iron heads in the 4.9 caused by inadequate cooling system maintenance...). Heater cores plug in cars with no supplement in them same as cars with supplement.

The supplement, as has been described before, is actualy tiny particles in suspension in the coolant. It does not dissolve, per se, but is just suspended. Over time and many trips thru the water pump inpeller the particles or fibers get chopped up to the point that they are just dust....and ineffective. That is likely what you are seeing as sediment in corners and quite areas of the cooling system. It doesn't hurt anything. Just the nature of the beast.

Do a forum search using "coolant supplement" and read my posts and save me some repeatitive typing, please.

blb
03-10-05, 01:22 PM
I would be interested to hear opinions on why GM specifies Bars Leak Suppliment for continuous use in their aluminum engines but why few, if any, of the foreign manufacturers believe that it is necessary in their engines. ( ie: Less casting porosity, better sealing surfaces because of tighter manufacturing tolerances, etc)

Maxoom
03-10-05, 01:51 PM
I think there is something that can be done to improve the stud to block transition so that the aluminum does not go to hell from some, so far undetermined, mechanism and allow the engine to be disassembled without tearing the threads.

Exactly. That's why I asked the question I did. Bob said he didn't know for sure and gave well-thought-out opinions on what might be going on (I think that proves he's not in the under-35 age bracket as someone suggested).


The specifics of my involvement with the Northstar engine over the years will remain a mystery on this board....sorry , but that is the way it is.

I understand this completely. That's why I said in my one-and-only post that I'm glad you're willing and able to post here. One of my life-long friends is a factory engineer for DC. He was doing the same sort of thing you are. His employer eventually discovered his identity and put a stop to it.

BeelzeBob
03-10-05, 02:38 PM
I would be interested to hear opinions on why GM specifies Bars Leak Suppliment for continuous use in their aluminum engines but why few, if any, of the foreign manufacturers believe that it is necessary in their engines. ( ie: Less casting porosity, better sealing surfaces because of tighter manufacturing tolerances, etc)


Too much is being made of the coolant supplement "requirement" in the Northstar for starters. GM is just more straightforward in their instructions since the sealer is installed at the factory it is recommended for service also. Other manufacturers that do not specify it for service still install it at the assembly plants.

The Northstar engine is designed so that there is little or no opportunity for coolant seepage into the engine oil cavity causing coolant contamination. If you look at the coolant passages and the lack of adjacent oil passages...or vice versa...you will see that coolant cannot leak into the oil. This is by design and diminishes the need for any sort of sealer to prevent coolant intrusion. The recommendation to use the coolant supplement in the Northstar is purely insurance against any incidental leaks due to porosity, gasket voids, surface imperfections, etc.... to the outside world...in other words, to avoid nuisance leaks onto the ground. I do not think the Northstar is any different from any other aluminum or cast iron engine in this respect. Very very very few of them do ever have a leak due to any sort of casting irregularity or porosity...but...for the few that do the coolant supplement is cheap insurance. Why all automanufacturers do not take advantage of it I do not know. I do know that a LOT of automakers do install the coolant supplement for such insurance. The parent company of BarsLeaks ships to a wide variety of customers in the OEM market.

There is no reason to use the coolant supplement in the Northstar for "conditioning" the coolant or protecting against corrosion or any other reason. Plain and simple it is an insurance against simple seepages and leaks that all cooling systems get from time to time, it is proven to be very effective and it is harmless otherwise, and it is very inexpensive. What's not to like..???

The 4.1/4.5/4.9 engine was a different story. The use of the supplement is considered mandatory in those engines due to the fact that the engine design is such that coolant CAN leak into the oil at the head gasket interface to the deck surface. If not detected and corrected, the coolant intrusion can cause depletion and contamination of the oil and subsequently cause extensive engine damage. That is partially due to the design constraints of the pushrod engine and the closed valley required for the lifter gallery. The early 4.1 engines were found to be somewhat less than robust in the head gasket to inboard deck surface sealing and coolant intrusion resulted. That is the application the supplement was tested extensively in and it was proven to alleviate the situation completely.

So...the coolant supplement is considered mandatory in the 4.1/4.5/4.9 due to the engine design and the possibility of coolant intrusion into the oil. This "mandatory" use in the 4.x engines and lack of understanding of what the supplement does causes confusion with it's recommendation in the Northstar. No harm will come to a Northstar engine if the supplement is not used...you just may have to chase and deal with a stray coolant seepage or leak on some cars some time in it's life. It is just a convenience item...not a protection for the engine like in the 4.x pushrod engines. I think a lot of people on see the "requirement" for sealer on discussions about the 4.x engines and see the similar service recommendations for the Northstar and lump the two together.

If a manufacturer has an engine design (like the Northstar) where the coolant cannot seep directly into the oil and contaminate it then the use of a sealer or supplement would be purely optional (like the Northstar). Where the engine design could allow coolant intrusion the use of a sealer is generally required in the engine service requirements. It is required for this reason in a lot of different engines made by a lot of different manufacturers.

It is worth noting that all the casting and machinings for the Northstar are leak checked with a via a pressure decay mechanism when the parts are manufacturered and the complete engine is supjected to a complete leak test of the entire assembly...including checking for leaks from the coolant cavity, the oil cavity, cross cavity leaks, etc. Any and every diecast aluminum part has porosity in it and on occasion porosity can cross link AFTER the part is completed and machined once it is thermal cycled several times in service. Having sourced parts from the same suppliers as many of the foreign manufacturers use they have the same "problem" with an occasional seepage from porosity opening up once it is heated up and cooled down several times. We just acknowlege that possibility and put the sealer in as insurance and as a customer satisfaction item.

Since service recommendations are rarely stated with optional type instructions...no need to creat confusion in the customer's mind...you either have to do something or you don't is the approach taken. In this vein, the coolant supplement in the Northstar is called out as a required item at cooling system service. Note that the Northstar service literature calls for only 3 of the pellets (a minimal dose for effectiveness) where the 4.1/4.5/4.9 needs to have 6 of the pellets ( a heavier dose to ensure complete effectiveness). I personally recommend the 6 pellets for both of them to ensure there is adequate protection against leaks.

Hopefully this will help with the confusion...??

Spyder
03-10-05, 02:45 PM
Lets face it, not many of us have the capability to drop the drive train in our garage. I also understand the restraints given the engine size and space to put it in. I guess that's just the price of progress. I can't wait for rear wheel drive to become the norm again and have an engine longitudally mounted, the way God intended :)

I know that all the service manuals and such say you have to go out the bottom...I replaced the engine in my 94 STS through the hood...the hardest part was reconnecting all the ac lines we pulled out of the way to make sure we didn't damage any of them. I still have to do that, actually, as I needed the car right then and now I've been putting it off and putting it off, and its starting to get hot again...hope it still works !? But it is very possible to r&r the engine from the top...pull the fans and the intake, take the tranny bolts out, drop the exhaust and its ready to go!

BeelzeBob
03-10-05, 02:50 PM
You know, gmt2u, I am somewhat of a bullshitter myself so I really enjoy listening to an expert. Going back and reading your posts makes me realize that I am in the presence of a master. I am still trying to understand what some of those paragraphs say.....LOL LOL LOL LOL

Please don't take my silence on this post from this point on as a lack of concern or disinterest. Just the opposite. It seems the fun is just beginning...but...duty calls. There is a ton of snow in Northern Ontario and I have far too few miles on my snowmobile this year. Leaving for Canada when I click the submit button, here, pretty shortly. Be back sometime next week. Lots of vacation days to use up....LOL LOL LOL

Later dudes.

haymaker
03-10-05, 03:08 PM
I hope you have a good vacation in the snow bbob. Look forward to your return.

dkozloski
03-10-05, 03:19 PM
My experience is just the opposite of Bbob, I spent an awful lot of time wrenching and machining but I am capable of and have done some engineering. My work experience encompasses about four or five different careers, each of which I excelled in. I hold a Supplemental Type Certificate for approval of the installation of a larger fuel injected engine in an aircraft, an aerial hotrod so to speak. The process from inception to having the certificate on the wall took five weeks. Ask anyone in the aircraft racket if they can match that. The process usually takes 1 to 2 years. I did all the strutural analysis and testing as well as fuel flow, air intake system cooling design and accessory validation. My partner did the flight testing. I can understand the math and have the life experience to know when an engineer is blowing smoke. I have had the unfortunate experience of having to tell an old and respected workman that his work consisted of thirty years of undetected crime. It's not the years of experience that count but what you have done with it and how you have learned to filter out all the noise and focus in on the kernels of wisdom after you have discarded all the chaffe. Bbob doesn't blow smoke. There has been a lot of noise lately about faked data in the scientific fields. Engineers who fake data soon find themselves homelesss on the street or in the penitentiary because you can't over rule laws of nature with an act of congress or wishful thinking. The only thing an engineer has to insure his job is his integrity. He can only sell it one time because then he doesn't have any.

1996deVille
03-10-05, 05:44 PM
Bbob,

Thanks for the answer to my BarsLeak question - I don't mean to make you type so much... I do appreciate the time and energy in the reply!

RAD
03-10-05, 08:43 PM
>" It's not the years of experience that count but what you have done with it and how you have learned to filter out all the noise and focus in on the kernels of wisdom after you have discarded all the chaffe. Bbob doesn't blow smoke. There has been a lot of noise lately about faked data in the scientific fields. Engineers who fake data soon find themselves homelesss on the street or in the penitentiary because you can't over rule laws of nature with an act of congress or wishful thinking. The only thing an engineer has to insure his job is his integrity. He can only sell it one time because then he doesn't have any."<[/QUOTE]

Well said dkozloski. I know íbbobynskií personally as a friend and fellow engineer, and although in an entirely different realm (electronic warfare, 30+years) we subscribe to the same disciplines and philosophy both personally.and professionally. Far from ďblowing smokeĒ bbobynski takes great care to publish the most informed, accurate information possible with no personal gain in mind. He is altruistic in many ways, this is just one example.

Although I do read quite a bit of the exchanges on this forum I post rarely, for the most part because my Cadillacs are just that reliable and trouble free.

I might say, being a life long aviation fan, and having a good deal of experience in the profession of avionics and piloting, I do enjoy your posts very much.

Keep up the good work.

Bob

cl1986
03-10-05, 09:49 PM
I'm not looking for any "standing" whatsoever on here. I was looking to spark some discussion into improvement of the longevity of these motors.

Wow, i thought 300k was pretty good. What are u going for?

dkozloski
03-10-05, 11:23 PM
If you want a record to shoot for, in 1961 I worked on a Kenworth truck that belonged to Lynden Transfer of Lynden, Washington that had 3,500,000 miles on it and had averaged over 600 miles per day since the day it was built and most of the miles were driven on the Alaska highway before it was paved. The truck was in good shape and appeared to me to be about mid-life.

gtm2u
03-11-05, 04:29 AM
...
I would guess that it was stiffer than normalized 4130 steel.
...

I have done much Tig welding of magnesium in the field. If you lose your gas envelope for an instant the weld is contaminated and the part is ruined. It's easy to spot though because you can see the black smudge and the white powder when it happens.
...

As I said, outboard motor manufacturers use alloys from the group called "white metals" that feature magnesium as the parent metal but alloyed with aluminum. What I didn't mention was it can also include zinc. At this point they start acting like pot metal and giving trouble from puddling and slumping issues.
...


Did that Mag alloy tool well?
...........
Yes, I've seen amatures attempt to make repairs on Mag automotive parts and they ended up ruining them. If they had used the cardboard box that you used it would have made all the difference in the world. I'm surprised that you got away without using lineman's rubber gloves which I suggested to the people after they ruined the parts. I have never done any TIG, MIG or Heliarc welding because I didn't have the equipment so had to have someone else. I was one of the few mechanics that could even arc or gas weld and braze cast iron.
........

The only "white metal" I have ever known is Babbitt which is used for automotive rod and main bearings. It came in bar stock maybe 1/2"x1/2" x 10" long, we used one of those big soldering irons for soldering radiators... you remember those days... right). We would "tin" the iron by first putting a small shaving on a "tin can" lid or bottom and rub it around for a few minutes to get a tin rich alloy which we then would apply in a thin layer to the steel rods and mains. Using the bar stock we then built up the thickness to the point we could bore them out but the final fittings were done with bearing scrapers.

I can't imagine that any of the metals used (tin, copper, lead, and I think antimony) form an alloy with Mag. Not spent a lot of time with outboards, but do know the big V6s use some pretty stout stuff. I don't think VW ever used Mag in their cases but for sure Porsche did even in the 356 series and of course their racing engines. It was the 356s that gave us fits with torn studs both mains and heads. Southern Ca was the sports car capitol of the world and along with that are mountains and high deserts which can get quite hot in the summertime. These just wouldn't take the punishment of of running 90-100mph for long periods in those temps even with the Mag alloy. The VW owners were a bit more sane and you could get them to listen. Once it became a "used" car it rarely saw a dealership for repairs until major disaster. I had a customer who's father knew the "auto shop" teacher and as friend he rebuilt the engine. It lasted about 300 miles when they brought it to me with a couple of bent valves. Quick fix and out the door, week later here she is again same problem but now it's got bent pushrod tubes. I scold her about her driving habits, the shop splits parts and labor and it's back on the road. G.D. three weeks later here she comes again except this time it's on the back of a tow truck, oil everywhere from broken pushrod tubes. Valves bent at 90* and nasty dents in head and pistons. Hells bells I'd never screwed up an engine job in my life but my worst nightmare had found a home in my stall. The case is twisted and has to be bored, I Slimsert the damaged studs which must have stretched .100", 2-3 pistons and maybe even a rod. I get to looking at the heads and notice a valve guide isn't sitting at the same level. Holy cow, the shop teacher has cut corners and installed steel guides from who knows where. The factory had never heard of such a problem but I knew instantly what was going on. The girl would take a few of her classmates for a drive up in the local mountains the engine would get hot, the guides would slide out of their bores, cock the valve, smacked by the piston which would drive the guide back home but not before bending valves, pushrods and tubes. All because some shop teacher didn't know that aluminum expands 7x more than steel and failed to tell anyone that that he had saved them $12 difference between bronze guides and steel.

Back then shop teachers and school boards saw no reason to teach anything BUT American made automobiles. It took me 3 years before I convinced them the imports were here to stay and they were not doing their students justice and looking the other way when 25-30% of the market were imports here on the west coast so that's how I got my provisional teaching credential. It was probably another 5 years before Detroit got the message. Once I had that the job offers were coming in once a week from every prison you could imagine. Yegads, seems the prison systems were eager to actually offer _cutting edge_ technology to rehab the inmates. The only problem was they didn't want to pay and location was always in some place where I didn't want to be.

An interesting aside the space race was in full swing and Russia was cranking out PHDs left right and center but they neglected one minor detail they forgot that not everyone wants to be a Doctor of something. As it ended up they were paying auto mechanics more than they were medical Doctors. You are old enough to maybe have realized the difference between a mechanic and a Doctor is their patients talk to them.
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More
gtm2u





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gtm2u
03-11-05, 07:12 AM
...
I agree with a lot you have to say. I think there is something that can be done to improve the stud to block transition so that the aluminum does not go to hell from some, so far undetermined, mechanism and allow the engine to be disassembled without tearing the threads.
...
In the aircraft engine overhaul racket we used a sealer on the gaskets, not to seal the gaskets but as a release agent to make the engine easier to disassemble at the next overhaul.

I have to differ with you on the design of the block casting in the area of the bolt anchors. The Northstar looks to be a rendition of an open deck Deutz diesel done in aluminum rather than cast iron. Also there appears to be no distortion of the bores when the bolts are tightened which is the over riding design issue in this area anyway. How about some specifics from you on what you would change to address some of the problems that are appearing in the field. For instance, I would use studs with rolled threads in place of the head bolts but I would put the heads on first and then run the studs in to the appropriate depth using a mild interferrence fit. Then I would use hardened and ground washers followed by high strength spline drive nuts. What do you think?

I honestly don't know what's the problem, I have some ideas which include problems with the aluminum alloy and heat. We don't know if it's virgin aluminum or recycled beer cans. I remember when Nissan and Toyota used the same supplier for their A/C condenser and evaporator. It seems the supplier didn't bother to tell them they were using recycled aluminum. Well about 6 months into the car's use they started loosing freon, some just a little and some a lot maybe as much as a charge a week. It turned out that the aluminum was contaminated with some other alloy which they discounted as causing any problems so didn't bother to extract it. However between the heat and cold cycles the foreign alloy wouldn't expand and contract at the same rate and after a while it just wore molecule size holes in the aluminum. As for the caddy I don't know if we are dealing with 25k, 30k or 35k tensil strength for the cast aluminum block.

Now when you put 2 dissimilar metals together under pressure they will make a molecular bond and it does not require water for this to happen. However a small electrical current will speed this up. So if we don't have an alloy problem we certainly can consider that when you start to remove a head bolt it litteraly has to tear molecules apart. If the aluminum is weaker than that bond then thereads are ruined. But if you copper plate them it greatly reduces the molecular bond and what does occur is the copper yields and not the aluminum. I didn't make this up and I ain't smokin any funny stuff.

How am I doing so far?

If you didn't have to disturb those threads they might last 100 years, to get around that and yet be able to service the engine you install studs rather than bolts. But we still have the bonding problem of steel to aluminum. Simple, install the inserts, now you have the outside insert threads contacting the aluminum and the stud is steel to steel so we don't set up the bond issue and you don't have the copper clad.
.....................................

I spent an hour with a service manager and senior mechanic measuring every dimension of the bolts, the head and the start of the block thread and end plus the unthreaded portion of each hole. I don't have my measurments in front of me but the bottom of those holes to the best of my knowledge extended into those webbing bosses some place from 1" to 1.5". There is plenty of thread to go another 1/2+ but unfortunately I've not found a 35 or 40mm long insert.

Hello Huston we have a problem and what the factory keeps blindly telling us it it doesn't exist or their repairs are missing the mark on 1st repairs but they offer 2nd repair with a hole big enough for a Mack truck. I would be interested in knowing what percentage of failures of first repairs were caused by sloppy work which then has to be done again. But if that repair is just as sloppy as the first then we have a certain failure.

I have never actually measured pressures at time of combustion but the number I learned was 2000 psi and will soar to over 2500psi if you have detonation. These were numbers that were taken under jull load and not idle. Huston we have a problem and it's not getting solved, maybe if we have to err it would be best to be on the conservative side. Now it's getting a little edgy for the strain on the factory bolts. Not rocket science but you start to look for something else, so who needs stronger the big professional dragsters and the racing industry in general. Bingo 190,000 lbs tensil strength, treated and then rolled not the other way around. This has worked for me for over 40 years and I see no reason to change.

If I use the full length of the insert in theory it should get me in round numbers at least 20% more grip. What can we do with that, we can increase the clamping pressure a conservative 10% more.or if more adventuresom 20% for you have at least doubled the bolt strength.
......................

Would you recognize that head gasket "glue", how about SQ-32M? It came from their aircraft engines but starting with the S2 I think it was required. This was a long time ago and was #42 for a tube. After about 10 years it started showing up as silicon RTV

Cheers,
GTM2u

1996deVille
03-11-05, 12:46 PM
How much weight is being saved with the aluminum block/heads?

I think it would be interesting to drop a 4.3 Chev v6 twin turbo into this platform. Keep the cast iron et al, still have room to work on the engine, and probably have the same weight in the front end...

Stripped threads were/are a way of life in the Model Shop (Boeing). On critical joint structures we'd CNC a steel plug and thread it to keep away from tearing up the aluminum - since the part was already on the deck the time it took to do this was well worth the time saved in fixing the aluminum threads. We didn't have to worry about the expansion rates, however...

Time is money and I'm sure we could do things in R&D that production couldn't do... but, it only makes sense, once a platform is decided upon, to work out the weakest points for repair down the road and aluminum presents some major problems compared to its cast iron counterparts.

I never had the chance to work on the actual power plant during my 757/767 days. I was, for a time, next to the engine repair station and watched those monsters come in for maintence - but, alas, I never witnessed a complete tear down to note the weakness in the design and how the shop overcame them. And, our model changes happened once every 20 years or so... a lot of the same tooling was used from other models to build the new platform, so the designs that worked were kept alive.

I think, in the end, it all comes down to expectations. We purchace these cars with inflated expectations that they'll go forever and we'll never have any challenges with them! Kind of like talking with our fathers about the cars of the 20's and 30's as if they were "perfect," and of course, they weren't.

We are probably in the last decade of dino powered cars, so the N* platform will move into Cad history and the next evolution will be on the showroom floor soon. Then it'll be like 1900 again - and the learning curve starts once more...

I'll still have my '68 GMC 327 - it will be completely restored and it'll be VERY easy to fix, but, alas, no gas to make it go... but, for just a moment we can go back to the day when a set of wrenches fixed anything and there were no metric heads to worry about, and...

dkozloski
03-11-05, 02:58 PM
gtm2u, standard practice for air-cooled aircraft valve guides is phosphor bronze for intake guides and nitrided steel or high nickel cast iron for the exhaust installed with a heavy shrink fit. Some of these guides are flangeless and depend entirely on the fit to prevent movement. The guides come in oversizes and most shops just ream the heads for an oversize but I always liked to measure each hole and machine down an oversize guide between centers to get the fit. I replaced hundreds and hundreds if not thousands of guides and never had one come loose. Some times if a standard guide was going to be a bit loose I would take it over to my plating shop and put enough copper on it to make the fit. I see you have had about the same experience I have with VW and Porsche cases. I was never impressed. If you think you had expansion problems in the desert you ought to give them a try at -50deg.

blb
03-11-05, 04:45 PM
How much weight is being saved with the aluminum block/heads?


I've wondered the same thing. I'd gladly give up all of the unnecessary power add-ons (Road sensing suspension, air adjustable rear struts/compressor, climate control, ABS, etc) to save weight and have the engine cast iron block / cast iron heads if that's what it takes to eliminate the head gasket issues.

But, on the other hand, look at the LS1.... another GM all aluminum engine with NONE of the headgasket issues of the Northstar. I'd be interested to hear about the differences in designs between the LS1 and Northstar and why you just never hear about headgasket issues with the LS1 (which is presumably marketed to folks who are more likely to beat the crap out of it ie: Corvette and F- Body) than the Northstar (which is marketed more toward the more sedate older crowd.)

1996deVille
03-11-05, 09:42 PM
Blb,

I'm with you - I wish a person could still get a clean, basic model. I miss the days of having some control over what was/is ordered. I suspect it is easier just to build everything the same on the assembly line and let the buyer deal with the problems at hand.

I understand the new Buicks will get the N* this coming year...

gtm2u
03-12-05, 04:14 AM
gtm2u, standard practice for air-cooled aircraft valve guides is phosphor bronze for intake guides and nitrided steel or high nickel cast iron for the exhaust installed with a heavy shrink fit. Some of these guides are flangeless and depend entirely on the fit to prevent movement.
...
If you think you had expansion problems in the desert you ought to give them a try at -50deg.

These VW guides were 99Ę so you know they wern't nitrided. If I ever questioned guides I would use an automatic centerpunch and hit them in 3 or 4 spots. Whoever the maker was for those steel jobbies it took them a couple years before they pulled them from the market.

I think JC Whitney sold a gasoline fired heaters for them which could also be ducted to pre-heat the engine as well as the interior for "artic" conditions. I only remembering seeing a couple, I found one in a wrecking yard and switched it to diesel as a boat cabin heater.
..................

You didn't comment on the studs.

I have another approach, I'm going to try and do this in place without pulling it or the heads. I've caught blown headgaskets early on and found head bolts to be loose so I just retorqued to the high end and added 10%. It's bought the customer at least another year of not having to pull the head.

However it will require I drill the head bolt passages out .040" which will make them 1/2". Since the head design seems to be good with few reports of having to flycut them or other problems I can't imagine that 40 thou will change anything. I may have to weld an extension on the drill bit and the tap. Then I have to remove the falir on the insert so it will pass through the hole and into the block. What I've not decided on is the insert installation tool design, my initial thoughts are to cross drill a bolt or stud and install a roll pin.

Needless to say I can only do 1 bolt at a time and it will require more frequent cleaning. It saves me from pulling the heads and having to deal with the guide plate installation. I'm only guessing but think it can be done in 4 hours, if I can pull it off I will have saved a lot of time. If it doesn't work then I've only lost 1-2 hours since the inserts will already be in place and it's just a head gasket job.
.............

Has anyone done the repair without removing the subframe?? I came across a set of instructions which said to remove the front subframe bolts, loosen the rear and let the front drop down several inches. This will tilt the rear head away from the firewall enough for removal.

.............

What is the trick to removing the water pump housing/manifold rear 2 bolts??

Cheers,
GTM2u

1996deVille
03-12-05, 12:11 PM
GTM2u,

I have a shop manual for 1996 - what year/s N* do you need info for? I can make some copies and send them your way if you like.

Are you taking the entire water pump housing (bypass, I guess you could say) off the motor? If so, I can look in the manual notes and check disassembly procedure if you'd like... I think there are two very unique gasket/seal assemblies you'll have to purchase - when I was in the middle of my water pump job I ordered a complete set of gaskets and seals, used the ones I needed and returned the rest. There were two that had gasket material molded around a steel sleeve - like a spacer seal. I didn't have to go into the motor that far, so I'm not exactly sure where they're installed, just that at some point in the tear down you'll more than likely need these.

The more I dig into this motor, the more interested I become in dealing with the aluminum block/head design - I only wish the motor could be gotton to in an easier fashion.

My dad was an engeneer/draftsman. He also loved to wrench. If he had been involved in the layout process of this assembly he would've forced the design team to go through the rebuild process - but, alas, not many Cad owners want to rebuild their cars, just a few of us on this site. These cars have gone the way of most everything else in our world, namely that they are now disposable autos - run 'em untill they die and crush them into blocks...

A friend of mine had a 1960 Eldo and did a ground up restoration. That was one of the most beautiful cars I've ever seen and driven... those days are gone with this new stuff. Maybe, when I finish my GMC I'll go after an early '60's Cad...

Much success on your project!

gtm2u
03-12-05, 07:22 PM
GTM2u,

I have a shop manual for 1996 - what year/s N* do you need info for? I can make some copies and send them your way if you like.

Are you taking the entire water pump housing (bypass, I guess you could say) off the motor? If so, I can look in the manual notes and check disassembly procedure if you'd like...
...
the more interested I become in dealing with the aluminum block/head design - I only wish the motor could be gotton to in an easier fashion.

My dad was an engeneer/draftsman. He also loved to wrench. If he had been involved in the layout process of this assembly he would've forced the design team to go through the rebuild process - but, alas, not many Cad owners want to rebuild their cars, just a few of us on this site. These cars have gone the way of most everything else in our world, namely that they are now disposable autos - run 'em untill they die and crush them into blocks...
...
Much success on your project!

It's a '94 STS, I bought a 5 CD set which was reported to have all the info I needed but proved to be a big dissapointment. Thanks for the offer, may take you up on that. I'm smart enough to know that I will need a manual, just haven't found the right price just yet. :) I certainly don't need a manual to take the valve covers off and drill the heads to install inserts and studs.

My initial attempt to remove the pump was an absolute failure, the corrosion had locked the twist plate in to the dogs and wouldn't budge. Was in a hurry, couldn't find the tool local so made my own, even with 6' lever I sheared off the castles so started to remove the pump housing. Don't think it's a bypass but don't have a water flow drawing. The transmission shifting lever(s) are partly in the way. There are 4 paper type gakets, 2 for block & 2 for heads. The fire wall is close so cant swing wrench and other obstructions. I trid a factory type tool and that too would have broken so took a small punch and smacked the stainless plate a couple of times right at the casting, this was enough to break the corrosion loose and it popped right out. Not an issue at the moment if my stud job works.
................
I do think these design people should be held accountable for their work. However there are some other forces at play here which scares me, we don't see tool kits in cars anymore, we don't have auto shop in high schools so fewer skills taught/learned. You can't buy parts, you buy complete components and throw away a $500 item because of a $1 seal that they don't have to assign a part number or the parts dept to keep in stock for a 10Ę profit. You don't have mechanics any more, you have parts changers, who gets cheated... the customer. This is not limited to Detroit, the whole industry is geared for this mentality. If they could build a computer to fix these things they would make me obsolete so they could profit even more from their problems.

In other countries they made this mistake and found they had to recruit AND pay for skilled mechanics from other parts of the world just to keep common modes of transportation vehicles running. Yet have high un-employment because the government didn't recognize those needs. Here we pay CEOs 1000x what the average worker makes, can they possibly be 1000x smarter. We send people into space but then have to teach them which wrench to use to keep them alive. Sorry for the soap box but it does concern us as mechanics or DIY type people. It looks good on paper therefore it must be right, I've seen it here in this thread. I'm not struggling with progress, it's just that there are some important factors are being overlooked.
..................

I've had 3 caddys starting with a 1955 which served me well, an 1980 which was so-so and now this STS which I've not had a chance to drive but 500 miles but knew in advance it could be something besides the water pump. I know the potential is there to give me what I want, I am really impressed at the suspension and handling but when I fix things I also want them to _stay_ fixed and I don't have the confidence the factory has the answers or is wiling point us in the right direction. Other makers have built powerful aluminum engines that have been put in luxury sedans and all we got was un-informed crap (I don't like the word ignorance because it's not polite) when presented with how they achieved those results.

I will be madder than a wet hen if I find that the aluminum in this block can NEVER be made to accept my repairs because of some alloy problem which they don't want to admit. I have no desire to turbo charge or modify the basics save for the top end limiting electronics. I wan't reliability, I am resentful that it may require a week out of my life just to gain access to the lousy head bolts because of engineering.

The design lines are absolute classic especially if you like Pinnan Farina's work. There are a few things which might be improved as for driver ease but I don't have enough time behind the wheel to give formed opinions.

Cheers,
GTM2u

haymaker
03-12-05, 09:49 PM
Gtm2u, hello.

Looks like you are getting a good old taste of frustration. Hang in there youíll get it. I have already been through many of the same frustrations you are now experiencing when I time-serted and replaced the head gaskets on my Ď97 SLS. Sounds like you have been twisting wrenches for a long while probably longer than myself, boy how cars have changed over the years. When I first started I could slide around under many of the older cars changing parts with out jacking the car off the ground. I remember on my í55 chevy I could change the 3-speed transmission in 30 minutes and never need a jack. I got pretty good at changing transmissions and rear ends in that car because I broke so many of them 9 transmissions 3 rear ends and three engines. I loved to race, come to think of it I still do. The engine compartments in the old cars were roomy enough that I could climb in there to replace any parts that were hard to reach from the fender. You climb into an engine compartment in one of todayís cars and you run the risk of breaking a lot of parts with your body and the car in all likelihood will not start once you climb out.
I guess Iím still trying to figure why you want to change the head bolts to studs? When I had mine down I checked most everything and the bolts didnít fail. Fact is I fabricated a test fixture and tested many of the old head bolts 30lb/ft+ 240 degrees torque angle. I measured each test head bolt with a digital caliper before and after each tensioning test and they all came back to within 0.001 of their original pretest length. As to finding a way to install the time-serts with the heads on the engine, the first repair time-serts are not a surefire fix. Some people have posted of pulling the first repair time-sert out of the block during the head bolt tensioning. Iím sure you donít want to try and enlarge the head boltholes enough to install the big-serts aka second repair time-serts. There may be some on the forum that have needed to replace the head gaskets a second time after the time-serts had been installed but I donít remember reading any posts in which that was stated. In other words if the time-serts hold the same is true of the head gaskets. This of course is based on my time-serted engine and the posts I have read on this forum. Both head gaskets were blown on my engine front side between cylinders 2-4 and on the rear at cylinder 1 toward the timing chain cavity. I had one loose head bolt per side but they were not located around the problem cylinders.
Let me know if there is anything I can do to help and of course good luck.

gtm2u
03-13-05, 02:11 AM
Gtm2u, hello.

Looks like you are getting a good old taste of frustration. Hang in there youíll get it.
...
I guess Iím still trying to figure why you want to change the head bolts to studs? When I had mine down I checked most everything and the bolts didnít fail. Fact is I fabricated a test fixture and tested many of the old head bolts 30lb/ft+ 240 degrees torque angle. I measured each test head bolt with a digital caliper before and after each tensioning test and they all came back to within 0.001 of their original pretest length. As to finding a way to install the time-serts with the heads on the engine, the first repair time-serts are not a surefire fix. Some people have posted of pulling the first repair time-sert out of the block during the head bolt tensioning. Iím sure you donít want to try and enlarge the head boltholes enough to install the big-serts aka second repair time-serts. There may be some on the forum that have needed to replace the head gaskets a second time after the time-serts had been installed but I donít remember reading any posts in which that was stated. In other words if the time-serts hold the same is true of the head gaskets. This of course is based on my time-serted engine and the posts I have read on this forum. Both head gaskets were blown on my engine front side between cylinders 2-4 and on the rear at cylinder 1 toward the timing chain cavity. I had one loose head bolt per side but they were not located around the problem cylinders.
Let me know if there is anything I can do to help and of course good luck.

The frustration comes from the way it has been dealt with rather than state that information cannot be released.

Since we (and the factory hasn't released if they know) don't have the information the problem lies somewhere between the bolts action, clamping pressure, and the threads in the aluminum block.

For the loads imposed the thread pitch is too fine for aluminum this is supported by increasing it from 1.5 to 2.0. I don't know if they have increased the threaded length as well. My original intent was to possibly switch to a SAE coarse thinking I could find more choices in both inserts and studs. This proved to not be the case without going to some custom order. So for the moment I'm stuck with the factory inserts being a compromise for which the only thing I can do is increase the threaded length and a stronger metal which will NOT stretch.

My concern comes from the possibility that this is a cascading or domino effect. In other words first one thread tears or stretches because the bolt is too weak, after some time another is damaged etc. etc. By doubling the strength I will have eliminated the possibility that stretching at the thread is the root cause. All that is left is the wall thickness and thread length, by using studs I can extend to the full length of the insert and adjust at the nutted end whereas the bolt head cannot be adjusted. My hopes are to make this strong enough that it will act as a rigid unit so if it moves it will take out the whole unit rather than a little at a time over the course of weeks or months. It is far from the perfect or ideal solution but it is something I can try as a viable attempt with less posturing and more interest in solving the problem. I understand there is little motivation for the factory to be involved since most affected products are out of warranty.

I have not seen the 2nd repair insert(or is it 3rd?), I am told it's diameter is .609" - 613"(?) notes are a bit scattered. I did see another from a different supplier which must have been close to .750" which I didn't really entertain as an opition under any conditions. I may be all wet with this for the expansion of steel vs aluminum makes the hole diameter larger thus length would be less effective than diameter.

Some builders seasoned their engine and transmission castings after rough machining for 2 years minimum in open wood crates kept outside to weather. This relieves the stresses that are inherent with the casting process so when final machined, liners fitted, and other key componets added they know it has a better chance of lasting for many decades.

Cheers,
GTM2u

cadillacmike68
03-14-05, 03:21 PM
Bbob, talking about meticulous maintenance. Back when I was in the missile racket everything was offloaded from the ships periodically and sent to the depot for inspection and repair. Everything came apart and was inspected and tested. It was all sent back to the ship and inspected and tested some more. Reliability was always a problem. Then the Navy shifted gears and said "Let's treat this stuff like a round of ammunition". At this point it was carefully assembled, inspected, and tested one time and sent to the fleet. They were told to leave it alone and don't mess with it. Reliability rates went through the roof. I would bet that from the looks of the average grease monkey you see fooling with your car there is a heck of a lot that gets done to the car that does more harm than good. The Air Force found that the inspection of wire bundles in aircraft introduced more faults than it prevented. Put the cars together, seal them up, and don't let anybody with tools near them.

Back in college (1980), while I had a 1970 Fleetwood Brougham, I saw this sign at an auto electric shop (typical shop guy, gray haried, missing teeth, wife rasn the "office" and helped with diags, etc. but a VERY knowledgable shop):

Our laobr rate: $5.00 / hour
If you wait: $10.00 / hour
If you watch: $15.00 / hour
If you help: $20.00 / hour
IF YOU WORKED ON IT FIRST: $30.00 / hour :lildevil:

Remember that we're talking 1980, factor increases appropriately. Those guys kept my car running back then and educated me quite a bit.

cadillacmike68
03-14-05, 06:30 PM
DK,

You beat me to it - I can just see the day a shop guy lights up the welder to do a quick fix... yikes, it'll burn the whole dealership down!!!

What a waste of time for 24 pounds.

We'll soon be hearing of "spontaneously combusting BMWs" on CNN! :p

cadillacmike68
03-14-05, 06:42 PM
I've wondered the same thing. I'd gladly give up all of the unnecessary power add-ons (Road sensing suspension, air adjustable rear struts/compressor, climate control, ABS, etc) to save weight and have the engine cast iron block / cast iron heads if that's what it takes to eliminate the head gasket issues.

But, on the other hand, look at the LS1.... another GM all aluminum engine with NONE of the headgasket issues of the Northstar. I'd be interested to hear about the differences in designs between the LS1 and Northstar and why you just never hear about headgasket issues with the LS1 (which is presumably marketed to folks who are more likely to beat the crap out of it ie: Corvette and F- Body) than the Northstar (which is marketed more toward the more sedate older crowd.)

Are you kidding? Just wait a few more years, and the blown corvette engine woes will be all over the place in chevy / corvette forums!

1996deVille
03-14-05, 07:17 PM
As well as the new Mustang... disposable engines. I'm afraid I am becoming a fosil at age 48. Sigh...

blb
03-14-05, 08:30 PM
Are you kidding? Just wait a few more years, and the blown corvette engine woes will be all over the place in chevy / corvette forums!

Do you realize the LS1 has been in Corvettes since 1997 and F bodies since 1998? Eight years is plenty of time for an issue to become well known if there is one. And there just aren't any LS1 headgasket issues to be found. Now LS1 piston slap, that's another story, LOL.

cl1986
03-14-05, 10:14 PM
Alot of these LS1's have very low milage and are in mint condition.

Some of them are rodded to all hell and only made it to 60k. My good friend bought a 94 vette with some stumble or missing problems at 50k. It still fouls the one plug all the time, but it has most of its power. Many people that own these vettes just drive them and never even think, or know, somethings wrong.

Others have been in serious crashes at high speeds making lots of LS1 motors for old muscle cars.

I rarely see any LS1 vehicle for sale with over 150k miles on it.

blb
03-15-05, 08:37 AM
Alot of these LS1's have very low milage and are in mint condition.

Some of them are rodded to all hell and only made it to 60k. My good friend bought a 94 vette with some stumble or missing problems at 50k. It still fouls the one plug all the time, but it has most of its power. Many people that own these vettes just drive them and never even think, or know, somethings wrong.

Others have been in serious crashes at high speeds making lots of LS1 motors for old muscle cars.

I rarely see any LS1 vehicle for sale with over 150k miles on it.

The '94 Vette you are talking about, if stock, has an LT1 not an LS1. Many, many, F bodies are owned by teenagers and get the snot beat out of them daily with no headgasket problems and they are high mileage cars because the owner only has one vehicle. If you rarely see any LS1's with 150K, check out E-bay for '98 to '02 V-8 Firebirds and Camaros....

cl1986
03-15-05, 07:30 PM
Ya i did that before i posted, went to ebay found all kinds of cameros with 3.8 V6 with 190k or 170k, but no LS1, in fact i did a specific search for LS1 and they were all newer(93-99) cars with 20k to 60k on them.

BeelzeBob
03-16-05, 05:24 PM
hey gmt2u. I know you are not "speaking" to me....but....maybe you could post some more info about your 94 Northstar...

Is it currently experiencing a problem with the head gaskets or are you just starting this quest to reengineer the engine "just in case"...???

If your engine is really a 94 then it was filled at the factory with the green silicated coolant that needed replacement every 2-3 years/24-35K miles to keep the corrosion inhibitors in the coolant from becoming depleted and causing internal damage...such as failed head gaskets. If this wasn't done at some point in the engine's life then the lack of coolant maintenance is the likely source of your "problem"...not poor head bolt design or the need to stud the engine...and...if that is the case....studding it without replacing the gasket will do absolutely nothing to correct the issue.

If your head gaskets are starting to leak or you are considering them failed for some reason I can assure you that the factory recommended repair with the proper timeserts will be way more than adequate to run the engine for the rest of your life. Seriously.

The Timesert repair is a very robust repair and there is no need to reengineer the fastening system. I would heartily recommend that you do NOT drill out the head bosses for the head bolts for added clearance so as to try and install an insert without removing the heads. You WILL weaken the column of material that the head bolt bears against and cause it to collapse under load. This is particularily true if you do try to install some sort of stud and up the load on the fastener. Been there, done that. The column of aluminum that the head bolt bears against that must handle all the clamp load of the head bolt is not thick enough for you to start drilling it out for clearance...

Trying to install the inserts without removing the heads is very difficult. It will take you far longer to try and do this than to simply remove the heads. And, by doing it without removing the heads, you will not have replaced the item that is causing you the problem...the HEAD GASKET. Even if it is currently fine , the head gasket is not going to like having load removed from one bolt at a time and then reclamped with some sort of stud. You will do this exercise, then the head gasket will fail and then you will REALLY lambaste the engine not realizing that you brought on it's demise by your scheme.

If the engine is leaking or consuming coolant remove the heads, timesert the block, install new head gaskets and just put the thing back together the way it was originally designed with the production head bolts. The production bolts are capable of generating more load than the column of aluminum in the head can withstand anyway so adding more load or more strength to that area is futile, useless and completely unnecessary.

For all the good info you are posting and postive ideas it is hard for me to understand your logic, here. You are devising a redesign and fix for a somethat that you do not understand. You do not have any idea what might be wrong with your engine (if anything) so why would you launch into a redesign and repair without knowing if it will fix it. The head bolts in your engine are probably perfectly fine. If a fire ring around the combustin chambe is cracked due to fatigue/corrosion/old age then the HEAD GASKET is the problem...not the bolts and changing the bolts will not address the problem. Didn't your school of hard knocks teach you the logic of inspecting the problem and diagnosing the failure BEFORE starting to devise a repair.

You are simply reading all the internet gossip and jumping to a conclusion with all your bolt discussions and load analysis and such. Find out what the failure is and THEN address the problem. Common sense, at this point, indicates timeserting the block of a 94 would provide additional insurance against a stripped bolt when reassembling. I will bet you that when you dissassemble that all the bolts are still tight and will "crack" when initially loosened indicating that they are tight, still holding clamp load and not the problem.

As an example, one of the posters on the forum (he can identify himself if he chooses) had two Northstars with "head gasket" problems....i.e....consuming coolant internally, overheating, etc.... Sure case of the "head bolts" , eh... Wrong on both accounts. One was a cracked fire ring on the head gasket from corrosion and thermal fatigue and the other was actually a fine crack in the top of the cylinder liner causing the coolant leakage from the coolant jacket, between the aluminum surround and the iron liner and into the cylinder thru the tiny crack at the top of the liner. Fixed with an aneorobic sealant and running fine. Wasn't the head bolts in either case. So....think before you jump to your conclusions....and save yourself lots of time and grief and remove the heads and do the job properly...trying to insert and such thru the heads will be a lost cause.


Per some of the earlier comments....a manufacturer storing their block castings for two years in crates to "age" them before machining. LOL LOL LOL This doesn't pass even the most simple minded common sense test. Please tell me the source of this BS. Really, can you imagine having half a million blocks in storage and casting two years ahead of the use/machining schedule...?? FYI....aluminum can be satisfactorily "aged" or hardened and stress relieved by a post casting heat treat to T6 requirements. "Aging" for two years....LOL LOL....c'mon. I bet you really believed that Smoky really looked for an ancient block in a school bus to build his cast iron motors from ..... LOL



Also....the trouble with any ongoing product improvement is that people always jump on the new technology as "proof" that the older stuff or previous design was no good. Yes, the "new" Northstar head bolts are 2.0 mm pitch. That was an ongoing design improvement to make the interface stronger to handle the added load of more power...... There was knowlege that the supercharged motor would be build and based on the rear wheel drive engine so the added strength was incorporated into the base design.

Putting the timeserts into the block alleviates most of the "weakness" that might be inherent in an aluminum female thread since the insert is installed into the aluminum and locked into place without having any load on it in the process. The insert OD threads are not being stressed and there is no friction and rubbing between the male and female threads on installation. Once the insert is in place, the male head bolt threads "rub" or "wear" against the steel of the insert. This is why inserts are commonly used in places where frequent dissassembly and reassembly is required. The friction in the threads wears the aluminum threads. The aluminum threads are plenty strong and can handle the load but , after many rundown installations, the threads can wear and inserts are required. So, just install the ones alread engineered for the task and get on with it. No need to make this a science project all over again. The need for the inserts and use of them should be pretty plain by now. Just use them.

I really could care less if you waste a lot of your time and money trying to invent something new here.... I just want to make sure that others do not follow your lead and waste THEIR time and money chasing something that is really not necessary. I also figure that when your redesign fails you will steadfastly refuse to admit that it was because of the changes you made to the engine....and will blame the engine as being "irrepairable" or something. This has been discussed before as others have labeled it "irrepairable" and a "throwaway engine"....same people that never heard of the timeserts or bothered to read the service manual.


Also, peak cylinder pressures for run-of-the-mill spark ignited gasoline engines are in the neighborhood of 1250 PSI. The supercharged Northstar, which is a 100 HP per liter engine, makes around 1450 PSI peak cylinder pressures. That is why I used the number of 1500 PSI so as to use a round number that was on the high side. Nothing is running around 2000 PSI...much less 2500. The pressure spike during detonation is so brief as to be almost non-existent from a sealing standpoint. It does create a severe shock wave that rings the chamber and piston like a hammer hitting it but the effect on the sealing system is negligable until the continued effect of the shock wave hammers the open face of the head gasket fire ring after many hours.....


BTW....I am still curious as to your claim that the fastener industry has abandoned the torque-angle tensioning strategy....any more insight on this claim..???

95Concours
03-16-05, 06:09 PM
This thread has become a frickin avalanche, lol..... :histeric:

Loose screw
03-16-05, 09:05 PM
It had been previously mentioned that one of the reasons against the factory using studs in place of the head bolt was the problem of aligning up all those studs with the holes in the heads without the danger of the studs touching the surface of the heads. A solution would be to install the heads first then install the the studs through the heads (just as the bolts are done) and then tighten a nut on top after the studs are set. For repair purposes it would aid machanics if some of the studs tops were at different levels so you wouldn't have to get them all aligned an in the holes in the heads at the same time. This could be done with different length studs or slightly adjusting the depth of the studs in the block. Studs could be easily used and the few difficulties associated with using them could be easily eliminated or serisouly reduced.

BeelzeBob
03-16-05, 09:34 PM
It had been previously mentioned that one of the reasons against the factory using studs in place of the head bolt was the problem of aligning up all those studs with the holes in the heads without the danger of the studs touching the surface of the heads. A solution would be to install the heads first then install the the studs through the heads (just as the bolts are done) and then tighten a nut on top after the studs are set. For repair purposes it would aid machanics if some of the studs tops were at different levels so you wouldn't have to get them all aligned an in the holes in the heads at the same time. This could be done with different length studs or slightly adjusting the depth of the studs in the block. Studs could be easily used and the few difficulties associated with using them could be easily eliminated or serisouly reduced.


I guess you need to define "easily".... Keep in mind that engines built in volume on an assembly line do not allow for extra parts and time to stay in the "easy" category.

The Northstar head bolts are very error proofed with the washers (necessary to bear the load from the head of the bolt and provide a surface for the bolt head to turn against) simmed to the bolts to keep them from being misplaced, lost or left out....no loose parts in other words. This makes each of the head bolt fasteners "one" part to deal with. If a stud was to be used....the stud would have to be installed at some point and torqued down. Assembly line techniques do not allow for double nutting studs to tighten them into the block holes like you do in your garage....some sort of detail would have to be formed in the end of the stud to allow it to be driven into the hole and tightened. Then....a separate washer would have to be installed over each stud and then a separate nut would have to be installed and started.... Too tight to finger start in that area so a tool would have to be used. Two extra parts per stud to be dropped, misplaced, forgotten, etc... Then alignment to the multiple spindle head bolt tensioning machine would have to be considered and alignment and engagement of the nuts. Bolt heads have tapered features to allow alignment and engagement of the sockets that nuts could not have.

In other words....dropping 20 head bolts into the holes and letting the automation tighten them is a pretty straightforward, error proofed arrangement. Installing studs just got WAY WAY more difficult and impossible to error proof. Error proofing and simple assembly techniques make for goor, repeatable quality...not a lot of small, loose parts. Studs would never be "easy" in any sense of the word in a passenger car engine.

Besides, the assumption that is being made that studs would be stronger for some reason is in error. The fact is that they are not stronger. There is simply no reason to think that studs are ultimately stronger or carry more load or anything. Studs wear longer in racing engines that are torn down more often and there is a slight advantage that the studs do not turn against the female aluminum threads...the steel nut turns against the steel stud. But, for the first 4 or 5 bolt installations this is a moot point. The steel/metallurgy/heat treatment of the head bolts is just as stringently controlled as the steel of studs and neither has a strength advantage or tension advantage. Any metallurgy that can be made into a stud can be formed into a bolt head. So...what is to love about studs. Nothing. Period. No strength advantage has been put forth and there is really nothing to lust after studs. Studs are used in racing engines to deal with the repeated assembly/dissassembly issues. They are also used as specialty studs can be easily fabricated to any length using the premade barstock so that engine builders can get custom length high strength studs easier than they can have custom bolts headed and made for the application. Simple logistics that do not apply to this situation. Studs have a very romantic image due to the "racing" connotation but they are used for a reason that has nothing to do with the ultimate strength in the joint.

zonie77
03-17-05, 12:44 AM
gtm2u, I've done 2 headgasket jobs and have a 3rd waiting. Don't mess around! Drop the cradle out. It makes it so easy to work on you'll enjoy doing the gaskets! (Just Kidding! :lildevil: )

You're either going to fight it by trying not to pull it all the way out and be miserable or pull the cradle and have it in a reasonable position to work on. I recommend pulling it.

Dooman
03-17-05, 09:02 AM
My 99 STS engine was removed from the top when they did my headgaskets. I did not personally witness it but it was done between my coffee and lunch..

zonie77
03-17-05, 09:56 AM
Bbob,
I'll bet you all the change in my pockets (Ooops, don't have any on now!) that the story on "aged" blocks was made up to justify using used blocks.

I know enough people that have headgasket problems on various brands, European, Japanese, and American. About the only unique concern I see is the timeserting. On the first one I did we found the rust on the firering, so I agree with the root cause. I think the manufacturers should be recommending changing coolant more strongly. But their emphasis is on less maintainence, not more.

cadillacmike68
03-17-05, 11:34 AM
Do you realize the LS1 has been in Corvettes since 1997 and F bodies since 1998? Eight years is plenty of time for an issue to become well known if there is one. And there just aren't any LS1 headgasket issues to be found. Now LS1 piston slap, that's another story, LOL.

Yeah, but in what numbers???? maybe 5,000 - 10,000 per year TOTAL compared to 150,000 THOUSAND or more Northstars per year for 4 more years of production than the corvette LS1 ??????:suspect:

cadillacmike68
03-17-05, 11:43 AM
"If your engine is really a 94 then it was filled at the factory with the green silicated coolant that needed replacement every 2-3 years/24-35K miles to keep the corrosion inhibitors in the coolant from becoming depleted and causing internal damage...such as failed head gaskets."

Not only that, but with every coolant flush, there should have been 3 of the GM cooling system supplement tabs (the ground up ginger root and walnut shells) added to the system to prevent casting porosity leaks.

Loose screw
03-17-05, 11:53 AM
I guess you need to define "easily".... Keep in mind that engines built in volume on an assembly line do not allow for extra parts and time to stay in the "easy" category. ...

.... Studs would never be "easy" in any sense of the word in a passenger car engine.

...Besides, the assumption that is being made that studs would be stronger for some reason is in error. The fact is that they are not stronger. There is simply no reason to think that studs are ultimately stronger or carry more load or anything. .

I have never had a stud pull out threads.... perhaps you or someone here has had some or even many but I bet it is a very small percentage compared to bolts pulling out threads.. I am sure it must happen... but I have never experienced it. I have had them strip, break and in other ways fail - but I have never had any pull out threads. And with so many manufactures using the softer and weaker materials I believe we can expect the problem will become far more common as these engine get older and/or require other service and disassemble that results with the thread will not be reusable.

As for studs being easy... your right it is a relative term - as easy as bolts NO, but not problematic but very doable and well worth it and far easier then having to tear the eangine down to repair the threads by Time-Serting them at a later date to save the engine. Just think of the reputation the N* would have IF there were no thread pull outs - that is worth something and worth the small but extra effort studs would require. Let the cheaper cars and engines use bolts - but in a N* I would expect a higher standard be used when reasonably possible and studs in these critical locations certainly are.

As for extra parts the nuts can be designed to have a washer built into them of course. And I would have to believe that totally automated assembly systems are so good now a days that getting the nuts on straight and not cross threading them is not a common event and not a frequent problem any more - but that is an assumption on my part.

BlueMoon
03-17-05, 01:03 PM
I've been sitting back and watching things progress into different head bolt failure
theories and I have to say that although I see alot of data coming out into the open, my original points seem to be far off into the distance now...The cooling system and running temps.

So far, it is very apparent that:
- The tensile strength of the head bolts are sufficient for the clamping force required.
- The bolts themselves are not failing. It's the soft aluminum threads in the block(needing to be replaced with the timeserts).
- Changing over to studs will NOT change the weakest link in the "chain"...the soft aluminum block threads
- Bars leak/sealant pellets are supposedly required for surface and machining imperfections and "porous" aluminum...HARDLY! It's to try and get more "usability" out of the headgaskets from all the movement!(Dont tell me we're trying to keep our engine block's paintjob from bubbling from "porosity" now are we? LOL). The whole reason we use gaskets are because of surface imperfections. If there weren't any, we'd be bolting metal to metal. (Gaskets are also used for absorbing expansion differences as long as we're on the subject too)
- We basically have a sealing/clamping issue here.

While everyone was off figuring out newton-meters and the clamping force for each head bolt a few very important things were NEVER mentioned...

First,
It is a given that aluminum expands more than steel. And... not only does steel expand less(the head bolts), they dont "follow" the block temp closely either since the only parts of the bolt making contact are at the head and at the threads(there is an air gap between the shank of the bolt and the cylinder head itself). So no matter whose engine it is, an aluminum head(or maincap) on Any substrate block is gonna expand & push itself AWAY from the head of that bolt further and further the more heat that is applied to it. While all of this is happening, those steel head bolts are trying to keep the heads on and with proper gasket/sealing pressure. But they are literally trying to be yanked out of the motor since they don't expand as much. So the thread pressure/bolt tension goes up relative to temperature. Period.

So the hotter the engine, the more bolt tension and the more pulling force applied to those softer block threads. Too much heat and the weak link WILL "give" because NOTHING is gonna stop the expansion of that aluminum head. If you had a head bolt system strong enough, the heads WILL warp or in severe cases, they will literally crack. So no matter what part "gives" at a certain point, that gasket is eventually Not gonna seal anymore and leak. That is the noticeable end result.

Another thing that shouldn't be forgotten is, the hotter you get aluminum, the softer it is(as with Any metal)

(Anybody still with bbob on "The hotter an engine, the better it "lives""?)

Let's continue....
Typically you would want to apply an antiseize compound on Any steel bolt in an aluminum substrate. But since those two different metals are constantly moving & expanding at different rates(not "globally" bbob) you Need to threadlock those bolts. So even threads that werent damaged by thermal stress in use will be weakened/damaged when they're removed because of the combination of the threadlock and the cold metal welding(seizing). So you're stuck putting thread inserts in either way. If you don't, you're asking for trouble.

In other words, when going into this motor, you minds well "re-tool" all the threads or just throw it away...This motor was Not designed to be rebuilt. "The engineers" were looking to hit a "high mark" with longevity in these engines. Let's not forget that.

So let's get back to head bolt clamping & sealing "longevity"....

Something that was NOT mentioned in the past posts with ALL of those head bolt tension/load figures per PSI etc... was that all of those figures are/were done at ROOM TEMPERATURE. That's how things are "miked", measured and torqued when it comes to Anything having to do with machining/measuring/fastening/torque-ing metal on Any engine. So when things start getting hot(or cold), EVERYTHING changes. And YES, engineers try to account for those ranges, but too big a "range" and you WILL have problems.

Who has the expansion rate differences of aluminum compared to steel off the top of their head? Anyone? (I'm not kidding.) While we have all these figures up and running, let's figure out the increase in head bolt tension as temperature is increased from 70 to 195 degrees. Then, let's do it from 70 to 250 degrees and see how much More load is put on those bolts/block threads. I'll bet we see some Very interesting results. Also, let's not forget that the inner head bolt loads are shared between the adjoining cylinders in those figures.

Anybody with me in the "temp department" yet?

I don't doubt that the head bolts are within spec. If they weren't, then the people that ran their engines the hardest would be the ones with all the head gasket problems. Sure, adding a half an inch more of threads will help, and factory timesert/helicoiling would be Extremely time consuming and expensive on the flipside, but again, I see temps as the "weak link" with what we have to work with thread-wise(pun intended). I still don't see any reason for failure other than temperature(I also don't see a valid enough reason to run those high a temperatures). So this is my point of all of this in temp discussion.

Another thing I'd like to point out is that aluminum heads on an IRON block engines Do
eventually fail with the constant differences of movement. But the majority of even those engines are by Far outlasting the aluminum head AND block Northstar when it comes to head gasket replacements. Ideally you would want to use All of the same material/metal in an engine since they see large temperature and expansion changes. But you can't use aluminum bolts for obvious reasons. So again, the bigger the temperature range, the bigger the expansion & bolt pressure variations that have to be dealt with.

I agree with you Totally bbob that engineers take into account the temp movements from an ice-cold block at startup in Alaska all the way up to running temp in the desert. The head pressure against the gasket at subzero temps is gonna be less than it was at room temperature And... it'll be greaterer at 195,225 and even 250. My point of all this is that there is a "range" that the pliability of the head gasket and a range of the head bolt's/block's thread pressure is set to run between. But why not keep the range of the running temps tighter/lower? Hotter is better??? COMMON!!!

Timing belts are moving mechanical parts and should not be used as a replacement example to a headgasket. This motor was built with longevity in mind. Everything from metal cam chains(instead of belts) to the spark plugs. This motor's weakest link is in basic sealing technology. And it's a shame.

So as I said and maintain in my first post... ALL aluminum engines are More heat critical. And I also believe that the range/limit of the block thread operating strengths are being overly stressed and sometimes exceeeded by excessive expansion.

Just my 2 cents(or none to some)

Excellent posts! Thank You to everyone who's had input to this thread both informational and humorous.

BeelzeBob
03-17-05, 02:25 PM
Bluemoon....honestly I agree with most everything you say to a degree.... I guess the difference in opinion is whether the operating conditions are within the range of the design of the engine.

The term for the gasket's ability to accept the added load induced by thermocycling and "spring back" with sufficient pressure to maintain a seal is called the gasket's "resiliency"....it is considered, measured and definitely taken into account. Tear the head gasket apart and look at the stainless steel core design and you will start to understand how the resiliency of the gasket is designed and built into it. The core is designed as a spring that it meant to be squeezed and relaxed so as to maintain sealing pressure.

The loads on the head bolts are measured at room temp, cold temps, operating temps and severe overheat temps.... Once a specially ground bolt is installed in the head bolt location (the ends of the bolt are ground smooth and perfectly parallel) a sonic bolt tester can accurately measure the length of the bolt and from the stress/strain curve of the bolt (which gives the spring rate of the bolt) the load is accurately determined. The bolts are developed and measured thruout the entire temperature range that the engine can see to make sure that the bolts are sufficient, the gasket loads are sufficient, the threads are strong enough, etc.... Just making the point that all the operating parameters WERE taken into account from a design, development and validation standpoint. Not just based on calculations but also with hard data from test engines. The bolts aren't just measured or mic'ed at room temp...the loads on them are monitored continuously during test at ALL possible temperatures.

As an asside....there is even a spark control system that uses the head bolts as the feedback ssytem that is used during developement of an engine. Each of the bolts is fitted with a tiny, pzieo-electric transducer that sends out a voltage signal as the bolt is stretched/loaded. You can 'see" the loads on the head bolt from the cylinder pressure pushing the head away from the block. This is used to measure cylinder pressure as a means of feed back for the spark delivery routines. Measuring and using the head bolt loads during engine operation is common place so that you know that it is easily possible.

Yes, as the aluminum block and head expand they grow and add load to the bolts trying to hold them in place. No the bolts do not grow as much...but....THAT is specifically why the NOrthstar head bolts are 10 inches long instead of 3 inches. The added length between the head of the bolt and the threads (called the grip length) adds much more "springy-ness" to the bolt to allow it to stretch under high temps as the aluminum expands so that it does not exert too much load on the gasket so as to crush it beyond the range it was designed to operate in. The length of the head bolts in an all aluminum engine will always be as long as possible for this reason. Cast iron engines that expand much at the same rate as the bolts that hold them together do not need the long fasteners but the fact that the long fasteners are there indicates the expansion and growth factor were taken into account.

It is certainly fair to say that gasketing and sealing an all aluminum engine is more difficult than a cast iron one due to the added expansion of the aluminum vs. cast iron... This is stating the obvious...

Gaskets are not really designed nor included to account for "absorbing expansion differences....." . They are , as you say, to account for surface imperfections. Gaskets are designed to handle the expansion differences but they are not a fuse or aborbing device. The fasteners are designed to handle the expansion differences.

Certainly thermal fatigue (the loads induced by the changing temperatures and expansion and contraction of the metal) is a major factor in the wear and tear on the gasket. Just like a paper clip breaks if you bend it enough sooner or later the gasket will start to loose it's resiliency if it is compressed and expanded enough times thru thermal fatigue. Your original comments started with the observations of the coolant temp changing from 195 to 225 during idles and such. My comments and explainations tried to point out that that temp range is insignificant compared to the operating range of the engine's cooling system..i.e..from -40 to over 265 F. Theoretically, any change in coolant temp would thermally fatigue the metal and the gasketed joint for sure. But, practially speaking, if the joint is designed to accomodate the stresses induced from changing from -40 to 265 F repeatedly then changing from 190 to 230 is practically nothing and is nothing to be concerned about nor a reason to fault the cooling system and the inlet stat design and such.

Something will, in fact, stop the expansion of the aluminum....the bolts. As the aluminum expands it exerts more and more load on the bolt stretching it slighlty until the load of the expanding material reaches an equilibrium with the bolt load. With the correct thread engagement and correct bolt metallurgy this is perfectly fine and will cause no harm whatsoever.

""In other words, when going into this motor, you minds well "re-tool" all the threads or just throw it away...This motor was Not designed to be rebuilt. ''' This statement is a bit of a stretch I would say... Looking at the ENTIRE engine design and saying it is a throwaway and not designed to be rebuilt because the head bolt threads need inserting on occasion is pure BS. The head bolt threads are a minor item in the overall job of "rebuilding" an engine. It is very very common in the re-manufacturing of engines to insert threads. So common that it is standard procedure in many re-man operations. Putting inserts into every engine so that an occasional one could be repaired or re-maned without needing an insert is nonsense. 99.9% of the engines are bolted together and stay that way until the day the car hits the scrap yard. The virgin aluminum threads are fine for that purpose. If it needs to be dissasembled and inserted then there is the parts and procedure to do it. That doesn't mean it is "not designed for repair or rebuilding". All the timeserted engines get discussed here...all the ones that just get bolted together and live fine despite the dire predictions of expanding aluminum and aluminum getting soft get forgotten about.

BTW....all the 4.1/4.5/4.9 engines that get re-manned at the GM Service Parts reman facility automatically get the head bolt holes timeserted. That engine also has an aluminum block with head bolts directly into the parent aluminum. After some experience it was simply more expedient to insert the holes of all blocks rather than inspect and check and occasionally strip one at re-assembly. It is really no big deal to do to re-man the engine with inserts at the re-man volumes.

While I agree in principle with your comments I guess the other difference is in the practical application of the logic. If the logic proposed is correct then ALL the Northstars should be dropping like flies from head gasket failures....unfortunately for that logic they don't. Some do, for sure, at high miles. But a small number and they are repairable and continue to live on.

BarsLeak or the GM Coolant Supplement is added to account for any minor sealing imperfections, hose connections, porosity of the aluminum castings or whatever. Barsleaks will not seal compression leaks from the chamber and , if you read the repeated posts about Northstar head gasket failures, the typical failure mechanism is at the cylinder fire ring...where BarsLeaks does NOT work... so...the evidence does not support the flawed logic you present. A good example of the correct use of sealing technology is at the water crossover seals to the block and head. A substraighted gasket is used with a silicon beaded seal. Absolutely the best technology for holding load and effecting a permanent seal. Problem is that the silicon beaded seal technology requires a perfect surface finish. Any scratch or imperfection will unseat the bead and cause a minor seepage or leak. Perfect place for the sealer to function in conjunction with the silicon beaded "front line" seal. Aluminum castings and diecastings do indeed often have porosity that often doesn't open up until the engine is thermal cycled several times (so it is not seen by the factory leak tests on the parts) This might only happen in one out of a thousand or ten thousand parts....but....the sealer is there to prevent a nuisance leak. Proper use of the product.

Aluminum definitely starts to get "soft" with high temperature. In fact, aluminum starts to loose some of it's properties with local temps in the range of 450 F.... It is interesting that synthetic motor oil will operate and live at temps higher than the basic aluminum structure of the block and heads can withstand!!! People tend to think that putting synthetic oil in the engine will protect it from anything but, in fact, due to the softening and loss of structural properties of the aluminum the oil temp can only be allowed to get to 350 F max because of localized hotter spots in the aluminum and concern with the aluminum itself weakening. The thought is that synthetic should be good to almost 400 F (and it is in cast iron engines) but an aluminum engine cannot even take the maximum operating temps allowed with synthetic oil...!!


Hotter, within the defined operating range of the engine, IS fine. Your quoting of my statements makes it sound like I would recommend operating the engine at 500 degrees.....LOL LOL I said that engines were run and tested at continuous temps of up to 265 and they are fine and look great. That is within the range of operating of the cooling system without boiling and staying in that range will not hurt the engine in the least. Changing the operating range of the engine from 225 to 195 or so is miniscule to the overall operating range of the system and has little to no effect.

This exchange has been interesting. It would be interesting to have a beer and "switch sides" and see who could argue the opposing argument equally as well...!!!!

Maxoom
03-17-05, 03:26 PM
Man, what a great thread. I'll buy the beer if I can listen in!

Welcome back, Bbob. How was the sledding adventure?

winston4u
03-17-05, 04:14 PM
I can certainly agree that this is a very interesting thread, but I think there is one fact in this entire discussion of head gasket failure that has been completely ignored or perhaps overlooked. That is the basic design of the N* block, which is an "open deck"design. No doubt this cofiguration was chosen because the basic block is pressure die cast (as I understand it) and an open deck is the only way the die form for the cooling passages can be withdrawn after the block is cast. There are many aluminum engines made just this way, but what the open deck block does is expose large surfaces of the head gasket to the coolant in the block. In fact, what it does is make the head gasket the top surface of the block coolant passages. This being the case, it become obvious why regular refreshing of the inhibitors in the coolant is a necessity if corrosion of the back of the head gasket is to be prevented. Ignore this basic maintenance and its just a question of time before the depleted (and now corrosive) coolant will eventually cause the gasket to fail.
Closed deck blocks (which must be sand cast) do not expose their head gaskets to the coolant in the same way, but still suffer failure -- only in different ways. As an example, Ford's 3.8 L V-6 used in '95 Windstar's was notorious for head gasket failures -- so bad that they extended the engine warranty to 60K miles to cover customer problems. This engine was in production at the time for over 10 years and was a cast iron, closed deck design with aluminum heads. Yet, for whatever reason, the head gaskets failed in huge numbers between the 1 - 2 cylinders and the 4-5 cylinders. I know because I owned a Windstar that had the gaskets fail at 59,000 miles -- so no cost to me -- but I never did learn what caused the failure or what the fix was, if any. The repair cost Ford $1900 to the dealer and I didn't keep the car to see if the fix was permanent.
Anyway, my point is that open deck blocks, like the N* indeed have a design that makes them vulnerable to gasket failure from lack of attention to the coolant. Change the coolant regularly, as required, and there should be a minimum of head gasket problems. At the same time though, as my Ford experience shows, closed decks are no less prone to failure -- and sometimes they may even have a design problem that causes them to fail long before they should and the manufacturer has to eat the error. Obviously, the N* doesn't fall into this category so I have to quess that much of the whining is over engines that simply were not properly maintained. Moreover, the fact that many of the failures are at over 150,000 miles proves Bbob's point that the N* is a very robust design and can stand up to a lot of abuse -- just not forever.

BeelzeBob
03-17-05, 08:12 PM
Interesting comment about the open deck design.... Realize that the head deck surface forms the "top" of the cooling passages in the block. True, that the gasket is totally exposed around the perimeter of the cylinder and I suppose that this might make it more vulnerable to the depleted coolant. Even if the area of the head gasket exposed in the open deck area were to fail completely, however, it wouldn't affect the sealing areas of the head gasket as that part of the head gasket doesn't really do any sealing. The other things to consider are that the most highly stressed areas of the head gasket in an engine are always between the cylinders where the open deck design is modified so that the cylinders are siamesed together and the head gasket in that area is trapped between the deck surface of the head and the deck surface of the siamese area of the block so that it is segragated from the coolant. If a head gasket is showing corrosion effects of the core from depleted coolant it happens in that area as well as the open area of the coolant passages caused by the open deck design. Even closed deck engines have coolant passages that expose the head gasket to coolant and typically the head gasket will hang far into those coolant passages as the head gasket serves as a flow restrictor to regulate and even out the coolant flow to make all cylinders flow the same. Not disputing or putting down the idea you bring up...just some things to think about.

Every design is always a compromise. The die cast manufacturing process of the block does require an open deck design to pull the core that forms the coolant passages out as the die parts. One nice thing about an open deck design is that the coolant flow around the cylinders is uniform to the very top of the cylinder where the most heat is rejected to the liner and where the rings spend the most "dwell time" at TDC where sealing is critical. Keeping the entire length of the cylinder to the top "wet" reduces bore distortion which is good. A closed deck design would theoretically offer more support for the cylinder liner and isolate the head gasket from the coolant. More importantly, the closed deck would tie the outer edge of the block to the inner edge of the block adding some strength...but this doesn't seem to be an issue with the Northstar block design as there is no leakage or head gasket issues with the deck rail along the inner and outer edges so this is probably a moot point.

When the supercharged engine was being designed it was decided early on to make the block a sand cast block due to the much lower volume and the fact that it would be machined on a dedicated machining facility and would not have to fit into the NA Northstar machining center. The supercharged block required extensive casting changes to incorporate the additional oil passages for the piston cooling oil squirters. The block for the SC engine is also modified to a closed deck design for the addtional strength at the top of the cylinders with the boosted application at 100 HP/liter. That block has a ground deck surface and the matching deck on the heads has a microfinished surface. The head gasket is a multilayer steel gasket with an elastomer filler to allow the microseal for coolant and oil passages. The head bolts are the same bolts as are used for the NA engine tensioned to the same values....it has proven to be bulletproof even in excess of 440 HP for extended periods of time.....

dkozloski
03-18-05, 01:38 AM
Bbob, there is one interesting phenomenon of aluminum engines that as far as I know was first observed by Nickson's Machine Shop in Santa Maria, California. When a horizontally opposed aircraft engine has the parting surfaces repaired by lapping, clamping, and align boring the mains; there is a minimum deck height or distance across the engine from cylinder flange to cylinder flange that must be maintained. Arnold Nickson, the owner told me that he has repaired engines right to the minimum specification and sent them to the owners. Years later he got the same crankcases back for the same repair to be redone. He knew the engines were already done to minimum but rechecked anyway and was amazed to find that the cases have grown through use in a sufficient amount to repeat the repair. He has records going back decades on hundreds if not thousands of crankcases and has seen this phenomenon repeated over and over. Evidently over the years the grain structure of the metal changes from stress and strain enough to make the case larger. How do you like the idea of another variable thrown in your lap? FWIF, this company has enjoyed the reputation for decades of being one of the finest if not the very finest aircraft machine shop in existance. If they tell you something you can take it to the bank. Everything they do is documented in exquisite detail. Every measuring tool is calibrated to a schedule mandated by the feds.

gtm2u
04-25-05, 02:14 PM
hey gmt2u. I know you are not "speaking" to me....but....maybe you could post some more info about your 94 Northstar...


Tell me why I should bother? Other than a post or so by _dkozloski_ and some military experiences he had there was nothing I didn't already know. Instead of a civilized discussion it always turns into you tossing out insults as if I have my head up my back side. While you may piss me off you ain't going to bully me with repeated trash. Frankly because you have constantly clouded the issue with personal insults I don't find you to be that credible and your facts are certainly suspect. I'm sure you have some rational for this but it sure passeth my understanding how someone such as youself who should command respect has to resort to such nonsense. I came to this thread to learn something and I got zero, I measure a factory bolt thread engagement and I get a bunch of nonsense thrown in my face. I don't think you made a single post that was not laced with flaming insults to anyone who dissagreed with you or contradicted what you wrote. That's not free exchange of ideas, that you bullying anyone who deigns to report different information or observations.

The fact that I have been using Keenserts and Slimserts for 40 years should have told you something, whoosh I don't know squat about thread repair or studs but again you show your ignorance. The studs I have chosen are at least 50% stronger than the factory bolts and long enough to utilize all the insert threads and the nuts have built in washers. Whoosh part of the casting bosses don't prodrude outside the block, whoosh what the blazes are those protrusions in the "V", water passages fool... Just a constant barage of crap makes me not want to discuss the weather with you much less some feeble minded attempt to clamp the head down because the damned bolts tear the threads out of the block.

In this whole thread the bottom line it would seem you contention is there is no problem and if there were then just do as I say. That's not good enough for me, I've seen my share of factory screw-up and blanket denial even from Rolls Royce.

If I can put a stud in there which will take full advantage of the Timsert length which is 50% longer than what I measured from the factory bolt then that's what I'm going to do. I don't need your permission, I was hoping someone participating in this thread had done it. Obviously you were not the person to have asked or attempted to have an intelegent discussion since you had another agenda. It's good to be a company man, they pay your rent, but this isn't about Cadillac, this is about seeing how big a jock you can be in front of these pimpply faced kids.

You are as full of shit as a Xmas turkey, as I stated before you should stick with what you know and not what you don't because you just keep sticking your foot in your mouth. I have no reason to misrepresent what Lancia did, get on the frigging phone and ask. Man of your stature and position wouldn't be denied a phone call to Italy to find out if it's true. Man of your stature would know if you wanted to speed up the seasoning process you would chill it to -300 and heat treat to 300 before doing the final machine work. It seems that even some of your buddies are not buying some of your crap. I don't know what Fiat is doing since they bought out the Vatican's stock and took control but most assuredly that was their practice no matter how ignorant you are. I'm sure GM or Cadillac has a library, you do know how to use one... you need to catch up on your facts.

Sheeet man, if Detroit didn't do it it must not be true. This is the mentality of Detroit that allowed the import market to take away 50% of their income while they kept pretending imports didn't exist. But they could build cars with steering wheels that break off and shove the column through a man's chest at 25 mph. This is the same Detroit that used 6 different machine screw types to hold the sheet metal on a Corvair engine when VW did it with 2. What a bunch of horse puckey, the same GM that said a 60 degree V6 couldn't be built and balanced, the same V6 they gave to Ferrari. The same V6 that Ferrari stuck 2 end to end and made their V12.

What reliable source can I call to verify that you did anything more than sweep the floors at Cadillac. You can snow these kids but actually I think you have an inferiority complex which you manifest by being a bully but that's just my opinion. I've been online for 25 years and by far for someone who claims to be a professional engineer employed in a responsible position you call to question why you would get on any list and make a fool out of themselves displaying their ignorance. This would be laughable were it not for the fact you believe you know everything there is to know and willing, without any attempt, to asertain the validity are willing to call me a liar when I was at the factory and saw them when the American Lancia Club was there as their guests celebrating the 50 years of the Lancia Lambda. For several years I was the only Lancia importer and think I know a little more than you about the mark and how they built their cars. Your one authority was with some rusted out Fiat that had obviously been abused, course that never happened to any GM product. We got onto Lancia why... because I was citing that magic word studs which you were obviously not conversant so your assinine knee jerk was to discredit my posts because you didn't know squat. I've been working on aluminum block engines for 40 years and you got what, 15 at best. Just another phony jock on the internet.

GTM2u

steelhrd
04-25-05, 02:59 PM
since the time of inception of this thread until present my headgasket blew. the car is a 1999 deville with 104000 miles on it. i have owned it since 2001 and have maintaned it with great care. cadillac service told me 4000 dollars for the repair. i have talk to at least three people with similar milage and the same problem. there is a problem in design.

cl1986
04-25-05, 03:42 PM
Who the hell is this guy??

Hes not bashing bbob hes trashing out site!!!

He calls us all pimply faces kids. Hmm seems like most on here are over 25.

Just becasue someone works on alluminum engines for 40 years doesnt mean they know what they are doing. Ive seen people in business for 50 years and have no clue on running a business. Most things that take people 8 hours to figure out ive seen others do it in ONE. 40 years of work doesnt mean shit. If you do know what ur doing then fine. But leave us alone.

Go away.

BeelzeBob
04-25-05, 05:24 PM
Geez......I guess I pissed you off. Sorry. Too bad you only come around once a month or so. We could use this sort of intertainment more often. Not sure what exactly I said to set you off, other than asking what happened to your engine. The desire was an honest attempt to understand if you were trying to improve the design or to fix a problem with your engine. There is a difference. I wondered if you are having head gasket problems currently or just anticipating them from reading the internet reports.

The fact is that I do have a lot of experience developing these (and several other) engines and do have a fair amount of experience doing engine development, fastener and sealing development and a LOT of experience with dyno testing and gasket and joint testing. Not as much as your 40 years maybe...but in 33 years at GM and several years before that of general racing and high performance work I have been around, too, my friend. Around enough to not be bullied by you either.

If you REALLY read this forum you will see a number of situations where I have helped people with their problems, explained to them how to correct the situation and they have posted back many times with the successful results. Not to bad for an internet jockey....LOL. I don't see YOU answering many questions about the engine or helping others...just posting negative comments and tirades like the one above. I help 10 to 15 people a day on this and other Cadillac forums....far beyond what you are doing with your experience here.

If you really want to carry on an exchange of what it going on with the engine, settle down, start a thread on the specific topic that you want to discuss and lets discuss. This whole thing started with you making a lot of accusations about what is "wrong" with the engine...accusations that are wrong regardless of whether you believe it or not. If you read the replies without getting so upset you might find out that there is a grain or two of truth in them.

There is really no attack on you....just your never ending attack on the engine and the design....similar to the rant above. Pick a topic and lets discuss it. If you want to put studs in , fine. They will work. Just as good as the production fasteners will. Your insinuation that the production fasteners are inferior is simply wrong. I supplied the clamp load data that you mentioned and you ignore it and publish a rant about being insulted. Stick to the facts and the technical issues. If you take a dissenting opinion as an insult then I feel sorry for you. No one has personally attacked you at all....in fact, you are the one attacking...see above.


You mock the questions that I ask about the bosses and such....???....just answer them. They are straight forward questions. I look at the block and do not see what you are describing. Explain yourself better and maybe we can agree. Several others had difficulty with your observations of the block design so I am not the only one confused over your observations and conclusions.


You must remember, when you start posting what you want to do, I have no idea whether you are some 15 year old reading Hotrod and fantasing or a guy that could build the engine in his sleep. I supplied info in my original answers to provide a basic understanding of the situation assuming that you knew little or nothing about the situation. If that was an insult, then I am sorry. No one still knows what you know other than that you can spew out a lot of venom...see above.


From a technical standpoint, I don't care how much stronger the studs you chose are....the whole issue with the joint is the clamp load generated. There is insufficient struture in the aluminum parts to handle a great deal more clamp load (you will simply deflect the column of aluminum supporting the fastener) so putting a "stronger" fastener in the engine is pointless. As far as the threads and inserts...???....there are probably a lot of inserts that will work. I was simply trying to impress on you that the Timeserts would work, they are already developed for the specific application and tested and validated for you. If you want to use something else, go ahead.



gmt2u....I tried sending you a personal message with a contact number for me. You have chosen in your profile to not receive personal messages so I couldn't get thru. Enable personal messaging on the forum in your profile and shoot me a message. I think that we can come to a very reasonable agreement off line. Contact me....

dkozloski
04-25-05, 06:01 PM
One of the differences between the aviation and the automobile worlds is the the auto manufacturer is free to choose how he responds to an engine failure but in the aviation world the federal government, like it or not, is the ultimate judge. If the car maker feels he can live with some percentage of failures and keep the customers BS'd he is free to pursue that path but the aircraft maker is forced to fix the problem absolutely or the aircraft is grounded permanently. On top of that, in aviation there are records and reports of every failure no matter how small that are colated and published throughout the industry for everyone to see. Failure rates, failure modes and all other relavent data are the public domain. One failure of one part in millions of hours of operation in some cases is sufficient to trigger an industry wide investigation. I remember one Pratt&Whitney engineer asking "How are we supposed to predict a one-in-a-billion event?" If Bbob and Cadillac were required to publish exactly how many and what kind of failures they have encountered we could have an accurate picture of just what is going on. As long as they feel it is in their best interests to keep all their failure data secret all they have to do to keep putting the same stuff out the door is to "dummy up" and tell us we just need to trust them. You can bet that Cadillac has a pretty good handle on just where the problems lie. You can also bet that the bean counters have the biggest vote on what and how they get fixed.

BeelzeBob
04-25-05, 07:50 PM
BTW gtm2u.....I had a thought or two driving home about our discussion here.....

You attack GM for having failing products and so on and take a shot about how GM has lost market share and so on and make the point that GM's performance does little for my resume. Point taken. Yet, YOUR resume that you put forward is with Lancia....????.... Pardon me, but do they still make Lancia's anymore..?? I don't mean to infuriate you but, really now, it is not like Lancia, for whatever they did right, is eating GM's lunch....or ANYBODIES lunch for that matter. So, pardon me for making fun of Lancia or Fiat or anyone else...but stating what either of those did 40 years ago is not really that impressive either.

Another thought along the same line and getting around to the idea of cylinder head studs.... The companies that ARE eating everyone's lunch do not use cylinder head studs on any of their engines....hmmm...maybe they really aren't required or needed to seal up an engine. Despite all your protestations I have yet to see any modern production passenger car engines that use studs to hold the heads one. So, that is why I was questioning why you thought that they are necessary or even an advantage. I still wonder, explain it to me.

You implied that the clamp load of the Northtstar production head bolts was barely able to contain combustion pressures. I supplied you with data to the contrary. Never heard back. The numbers I gave you for clamp load are real data, not something that I dreamed up. And I have checked back with some of my "experts" in the fastener field (and they don't even work for GM!!) ....they are still using torque-angle, yep. It is not passe nor have they adopted different means of tensioning fasteners. So, what is "the way" to do it.

You make a lot of noise about what I don't know and what my motives are. I get on here to help people that have problems with their cars and engines. That is my main goal. I occassionally run across someone like you that is just not convinced that we might know a thing or two. If you want to talk, talk. Otherwise, please, let's stop the name calling and BS. Hey, even dkozloski and I occasionally agree and HE puts up with me to some extent so I can't be that much of an idiot...am I...??? LOL LOL

BeelzeBob
04-25-05, 08:14 PM
dkozloski....yes, there are some differences between the two industries.

You forgot to mention the fact that GM and any automaker ARE required to report warranty and failure rates to the Federal Government. It is done periodically. Subsequent to the Firestone tire deal with Ford, all warranty data is available to the government and the auto companies are REQUIRED by law to report specific failure rates if they exceed predetermined amounts.

The actual failure rate of piston engine light aircraft engines is abysmal if you look at the number of failures vs. the hours of operation. Passenger car engines are FAR FAR more reliable and the longevity is MUCH MUCH better. Piston engines in aircraft are REQUIRED to have a MAJOR overhaul every 2000 hours or less and many do not make it that far. I don't keep track of the TBO's of every aero engine out there but I do know a lot of them do not exceed 2000 hours. If automotive engines had to be completely overhauled to like new condition every 2000 hours there would not be enough garages in the world to do all the work. An airplane might fly for 20 years and not require an overhaul because of the low hours it sees in operation. Any given car engine will see 2000 hours of operation in a year or two depending on the use and the particular commuters driving shedule. If every car engine were torn down and completely rebuilt even every 3 or 4 years I doubt that we would be having this discussion. Many of the engines on this forum have 150,00 or more miles on them when people post in to complain about a head gasket or some other problem. At an average speed of 25 MPH, which is being charitable given the actual amount of idling and city driving in many cases, that engine would have 6000 hours on it at least....THREE times the TBO of an aircraft engine. I say recently an article on the Lycoming engine company. They were bragging about producing over 365,000 engines in their life. GM makes that many engines every month practically. There is just a little difference in the volumes and the use schedule here to start comparing the two...!!! There is also a MAJOR cost difference in the engines when you start comparing what one is held accountable for and not.....a 300 HP Lycoming or Continental will cost, new, what..??....$30,000.00 ??? For an engine that costs that much with that short of a life span I find it hard to feel humble about what automotive engines are asked to do and how they perform and their reliability and durability etc....

Lycoming is just coming off a huge lawsuit that they lost due to crankshafts breaking in-flight and killing people... They had to "recall" hundreds of engines, they had many failures in-flight and they ended up changing the crank design, supplier, etc...to satisfy the FAA. This is on an engine that they make 1000 per year..?? We are not talking head gaskets here, this was the crank in two (or more) pieces. If GM (or anyone else) had this sort of performance we would have been out of business long ago.

Also, keep in mind, that , despite an astronomical price tag and extremely low production rates, the aircraft engines are not required to meet ANY emission, fuel economy or noise standards. They run completely open exhausts with no catalytic converters, no air cleaners or induction silencing AND they still run LEADED fuel. Really, the picture for making aircraft engines the 'standard" to condemn GM by is pretty weak and fading fast.

Oh, and I forgot to mention that piston aircraft engines are so understressed compared to car engines it is laughable. A 300 HP aircraft engine is usually in the 500 to 550 cubic inch range....and making only 300 HP. A Northstar is making 300 HP out of 270 cubic inches and is probably just as reliable...!!!

Sorry to unload on you like this but I hear this argument way too often. It just doesn't hold any water.

It is like when Bill Gates said that the automakers were idiots because if cars had advanced like computers they would be getting 100 MPG and making no emissions and would cost $100. The logic that you would have to pull over every 30 minutes to "re-boot" and occasionally turn the power off to reset everything and push the "Off" button to turn the machine "ON" etc....seemed lost on him....LOL LOL

dkozloski
04-25-05, 08:21 PM
FWIW, I did a little Google search on blown head gaskets and found complaints about every car you ever heard of and some I'll bet you haven't. Rolls-Royce went through several variations of enbloc(head and cylinders cast together) and seperate head-crankcase designs for the magnificant V-1650 Merlin engine. Caterpillar Tractor Co., Detroit Diesel, Cummins, LeRoi, Hercules, Buda, Continental Red Seal, and host of other standards of the industry have all had histories of head gasket distress. If you want a challenge, try keeping a head gasket in an old straight-eight flathead Pontiac or Chrysler. Back when cars got 50,000 miles to an overhaul it was easier to keep the head gasket sealed and they still had failures. The guy that figured out the perfect solution for head to crankcase sealing, died before he had a chance to tell anybody.

BeelzeBob
04-25-05, 08:30 PM
. The guy that figured out the perfect solution for head to crankcase sealing, died before he had a chance to tell anybody.

Good points.

Would this guy have worked for Lancia...???....LOL LOL

This is a joke gtm2u....just kidding, really.

dkozloski
04-25-05, 09:22 PM
Bbob, you're trying to compare apples and oranges. Aircraft engines operate at far higher power settings than any auto engine. Your North* is loafing down the road putting out 40 or 50 horsepower to keep the average car at the legal speed and a 300 H.P. aircraft engine is producing 225H.P + for hours on end. Many are rated for and operate continuously at WOT. Meanwhile the aircraft is going 200 MPH and in the 2000 hours has traveled 400,000 miles. How many North*'s can you show me that pile up 20,000 miles/month and have been doing it for 15 or more years. The only way you are going to be able to get a North* to travel this far in a month is to load it on the plane.

cl1986
04-25-05, 09:30 PM
I really dont think that any engine runs at WOT for hours on end.

It may run at a designed speed for hours on end but not WOT. That was just dumb to even say.

Once in the air the pilot still has the throttle on like when he took off?? I dont think so, most planes fly at what 550 MPH cruise speed and could probrably go around 800 MPH. My numbers may be off but they dont run at WOT.

RAD
04-25-05, 10:08 PM
In fact, they do. For example, itís a common factorydyno exercise for a Northstar to run 300 hours at full load, full throttle then be disassembled for wear analysis (which is typically little to none).

Itís simple physics that props run very inefficiently at speeds over 450 mph, and are useless over 500. 800mph?? Thatís beyond mach 1. I donít think youíll find any pistons at that velocity. Unless the engine explodes, that is..LOL


Carrier based aircraft is another application for certain WOT, whether prop or jet. The pilots are required to wind up and hold WOT for a sustained period before and during launch, and again when trapping (landing).




I really dont think that any engine runs at WOT for hours on end.

It may run at a designed speed for hours on end but not WOT. That was just dumb to even say.

Once in the air the pilot still has the throttle on like when he took off?? I dont think so, most planes fly at what 550 MPH cruise speed and could probrably go around 800 MPH. My numbers may be off but they dont run at WOT.

dkozloski
04-25-05, 10:12 PM
For agricultural operators the throttle is an on-off control; wide open to takeoff and fly and closed to land. Other operations require more finess. The typical profile for me to fly from Fairbanks to Anchorge, Ak. is WOT for takeoff and climb to the cruising altitude which is ideally chosen to produce 75% power which would be about 7000 feet. Power would be reduced at the destination as required to keep the airspeed below the redline on descent. I have been doing this for almost 50 years. That is the point I was trying to make. Aircraft engines operate at very high power settings compared to auto engines. A turbo-charged aircraft would take off at WOT, reduce to 80-85% for climb and cruise at 75% for however long it takes to get where you are going. Some aircraft engines are limited to a maximum of WOT for 5 minutes and 90% continuous power and are operated at these limits. In comparison auto engines are putting out 15-20%, if that much, as you loaf down the road at the speed limit. Yes, Grasshopper, listen carefully and some day you too will know. Over the years there have been hundreds if not thousands of attempts to adapt auto engines for aircraft use. For anything other than puddle jumpers you can count the successes on your fingers. Currently there can't be more than one or two packages available that are certificated.

Ranger
04-25-05, 10:36 PM
Hey, who you call'in a "pimply faced kid"?

dkozloski
04-25-05, 10:59 PM
Bbob, I hate to be the one to have to tell you that there are very few pure-jet commercial aircraft flying in the skies over the U.S. A careful examnination on your part will show that they are equipped with an adaptation of the propeller called a ducted fan that produces the largest share of the thrust with air that bypasses the turbine section altogether. These are equipped with variable pitch blades and all the features of the old visible unshrouded props. I would have thought that an engineer would have been more observant.

cl1986
04-25-05, 11:05 PM
In fact, they do. For example, itís a common factorydyno exercise for a Northstar to run 300 hours at full load, full throttle then be disassembled for wear analysis (which is typically little to none).

Itís simple physics that props run very inefficiently at speeds over 450 mph, and are useless over 500. 800mph?? Thatís beyond mach 1. I donít think youíll find any pistons at that velocity. Unless the engine explodes, that is..LOL


Carrier based aircraft is another application for certain WOT, whether prop or jet. The pilots are required to wind up and hold WOT for a sustained period before and during launch, and again when trapping (landing).

I knew someone would say that. I wasnt talking about lab tests.

Yes, ag related equipment runs on a throttle but is limited to about 2400 rpm and i wouldnt call that WOT cause they LIMITED the rpms. The diesel motor limited to 2400 rpm can easily run at 5000 if unleashed.

Tractors run all day long at the LIMITED rpm. We had an old 3020 that could run at 3000 either cause it was made for road travel and/or someone messed with the throttle linkage.

These limited rpm engines can generate more power by simply turning up the fuel pump to flow more fuel, they dont run any faster just more power.

Point is, no engine runs at its maxed out speed for hours on end, and if the plane engine cant spin any faster thats do to too much resistance and lack of power, not really WOT at all.

dkozloski
04-25-05, 11:39 PM
cl 1986, WOT=wide open throttle. The throttle butterfly is in the max open position. Aircraft engines are designed for a redline RPM for mechanical reasons just like a North*. They just happen to be limited to lower speeds than an auto because conventional propellers are limited to tip speeds below the speed of sound. Full power is at WOT and redline RPM. Most engines are rated at continuous operation in this mode. As a practical matter power is reduced by reducing the throttle setting, the RPM, by climbing to a rarefied atmosphere or a combination of the above. You have reinforced the point I have been trying to make; you cannot directly compare aircraft engines to auto engines because they are designed for and operated to entirely different standards. If you try to operate an auto engine as an aircraft engine it will fail unless highly modified. If you try to operate an aircraft engine as an auto engine it will fail unles highly modified. This has been proven by actual use a thousand times.

dkozloski
04-25-05, 11:53 PM
If calling me a "pimply faced kid" will make me into one, be my guest.

cl1986
04-25-05, 11:57 PM
I agree, two totally different things.

But i coudl put a 2400 rpm limit on my N* and call that WOT then, there is really no difference.

THats just like a go cart. Take the damn governor off and you have a good ride. A lawn mower engine can run at 5000 rpm also with no problem, but they have it limited to 3500.

I assume the aircraft engines are also LIMITED.

You cant compare limited "range of use" rpm to an unlimited one no matter what. That said the normal range of a northstar is about 2-3k then.

mechanix
04-26-05, 12:02 AM
I kinda like the idea of head studs, and main studs too. I can't quote lab reports, or statistics or even numbers. But it seems to me that where strength matters...studs are used. Top fuel drag racing engines, as well as many diesel engines...Packard, Detroit, International, Electromotive and Enterprise come to mind. I actually considered using them in my N*, but decided not to because of the cost involved, and because there simply wouldn't be enough room to get a socket over the nuts down in those recesses.

The N* head bolt (and main bolt) weakness as I see it is simply the lack of steel inserts installed at the factory. Those cast aluminum threads just can't stand the vibration and still hold the torque for years on end. They crumble like month-old bread. And if you try to tap them out to clean them up, they just disintegrate altogether. I should be grateful I guess...it keeps mechanics in business! *lol*

dkozloski
04-26-05, 12:09 AM
Mechanix, I agree on your take on the studs. Studs are used on dragsters but more for convenience in the requirement for a complete rebuild after every run. I like the idea of studs run into the crankcase with an interferrence fit. From the manufacturers point of view however, they are looking for the best way to put together a one shot deal. Inserts and the like just add to the initial cost.

BeelzeBob
04-26-05, 12:13 AM
Bbob, I hate to be the one to have to tell you that there are very few pure-jet commercial aircraft flying in the skies over the U.S. A careful examnination on your part will show that they are equipped with an adaptation of the propeller called a ducted fan that produces the largest share of the thrust with air that bypasses the turbine section altogether. These are equipped with variable pitch blades and all the features of the old visible unshrouded props. I would have thought that an engineer would have been more observant.



OK....where did this come from. When did I say anything about jets or whatever. The "ducted fan" engines you are bringing into the fray are really jets with very high bypass ratios for noise control and emission reduction. What does that have to do with piston driven aircraft engines, huh...??? Where exactly was I supposed to observe what...?? Besides, I knew that...LOL. Next, I suppose, you are going to ask me about water injection in a turbine....tell him RAD.

While it is true that PISTON engine aircraft engines operate at higher power levels you are exaggerating. The HP rating of the engine is at sea level. Those engines operate at 5000 to 10,000 feet of altitude. They are making a fraction of their rated power at those altitudes so, in fact, they are loafing along, too. The engines are typically pulled back to 75% to 80% of power per the manfold pressure reading, which is way less than full power. The turbo-charged piston engines are actually turbo-normalized engines. They make little to no boost at sea level and use the turbo boost to maintain sea level manifold pressure at higher altitudes. THOSE engines do run harder, I will agree as they will be running at 65 to 70% of rated power even at altitude. But, for the majority of aviation engines they are running at very low power levels considering the displacement of the engines and correcting for the altitude that they are operating at.

It is pretty rare for any engine to run at full throttle continuously for hours on end....except in some boats.....and on the engine dynos.....and in airplanes the do run at fairly heavy power settings for long periods of time... Long for an aircraft engine that is, still short timers for automotive engines.


The reason that an aircraft engine can run at such heavy throttle openings for long periods of time is that it is far less stressed than a car engine at full throttle. A Northstar makes over 1 HP per cubic inch at full power. A piston aircraft engine makes about .5 Hp per cubic inch....much less stressed, so it can live longer. Truck engines do the same thing. Bigger displacement and less HP so as to be much less power per cubic inch.....only way to make them live. The highly stressed piston fighter engines in WW2 had TBO times of 200 to 300 hours tops so they were replaced quite often due to the higher stress.

Boats run at full throttle a lot. I have friends that every where the boat goes the engine is at WOT.....LOL. Peg the throttle and go. Marine use really is the worst duty cycle for an engine. They are run very hard all the time.

I saw a 4.0 Aurora engine run at WOT for 10.5 days one time. It ran full throttle, max power, 6200 RPM for 252 hours in one stretch in a car. In the process it set 2 world land speed records (that still stand) and 42 other international and national speed records. I have a piston from that engine on a plaque on the wall in front of me. Looks fine to this day. Interesting statistic...during that run the car went a total of 48, 500 kilometers and the piston traveled 7000 miles...up and down the bore. Amazing , the rings are about 25% worn after scrubbing on the cylinder wall for 7000 miles.


I can carry the arguement of automotive-aero power either way. True there are few successful attempts...but how many have REALLY tried...??? Precious few real attempts by professionals to turn auto power into air power. Porsche did it many years ago but it was not very popular. I would be one of the first to argue that auto engines are not designed for aero power due to the RPM that they are designed to operate at, primarily. Piston aircraft engines run at 2400-2800 RPM to keep the prop tips sub-sonic. An auto engine has to run much higher RPM to make the same power so a speed reduction drive must be incorporated which adds expense and weight. The cranks in auto engines are not designed for the harmonics of hanging a prop on them. They are simply designed for a different purpose. On the other hand. Bbobynski , himself, has flown in a Northstar powered airplane twice....helped package, plumb and design the installation. Pictures to prove it. Works great in the application developed. There are many many private, homebuilt air craft with auto power that fly very successfully. If the engines were THAT far off there wouldn't be thousands of them at OshKosh each year. There are thousands of auto/aero conversions that fly into OshKosh each summer so the engines are pretty darned reliable even doing something that they are not designed to do.

Besides, argue the point as much as you want but a car engine does a hell of a lot better job in an airplane than and airplane engine does in a CAR....LOL....I have NEVER seen one of those running around...but I have seen a LOT of car engines flying in airplanes.

BeelzeBob
04-26-05, 12:31 AM
cl If you try to operate an auto engine as an aircraft engine it will fail unless highly modified. If you try to operate an aircraft engine as an auto engine it will fail unles highly modified. This has been proven by actual use a thousand times.



Nonsense.

Operate a Northstar at 150 HP or .5 HP per cubic inch, which is just like an aircraft engine operates at (a 300 HP lycoming or continental is almost 600 cubic inches) and it will run forever. Run it at 75 or 80% power, which would be 115 HP roughly and it will run far longer than any piston aircraft engine, believe me. Piston air craft engines are way understressed due to their large displacement and much lower RPM. Still THEY blow up all the time. Every month I read the FAA accident reports and see engine failures. My brother is an FAA inspector and he tells me about an engine problem bringing a private piston plane down frequently just in his corner of the US.

I have seen thousands of auto engines flying in airplanes at OshKosh and Sun and Fun every year.

mechanix
04-26-05, 12:37 AM
dkozloski, I know this is off-topic, but did Buda make aircraft engines? When I was a young man of 17 serving my apprenticeship in the shipyard I would often hear a lot of the older hands extole the virtues of the Buda marine diesel. My dad had great praise for them as well. I never got the opportunity to work on any myself, and I think I only saw a photo of one once. I hear they were quite an engine though.

BeelzeBob
04-26-05, 12:39 AM
Studs are used in race engines that are torn down frequently because of wear on the threads. The steel nut on steel stud doesn't wear. Repeatedly threading male threads into the female threads of the block would cause much more wear on the threads so studs are used.

There is no reason that a bolt cannot be just as strong as a stud. The metallurgy is just as good and the bolt can be just as large as the stud, so there is no ultimate advantage in a stud purely for strength.

Studs are common in a lot of race engines, also, because special metallurgy studs are relatively easy and inexpensive to make to custom sizes to upgrade a bolt. A bolt could be made just as strong but it would cost FAR more to make the tooling for the bolt and then only make a few. Bolts are cheap and strong if you make millions of them. If you need the strength to upgrade a joint then a stud is easy to custom make and obtain. That doesn't mean a stud is stronger by design...it is just cheaper to make for a limited volume application.

Studs are also used in some race engines because there is no room to install a long bolt due to overhanging hardware in the cylinder head. The stud just peeks thru the head surface with just enough room for a washer and nut. This is a difficult assembly but is OK for a race engine.

dkozloski
04-26-05, 01:05 AM
Bbob, I believe you exaggerated a little. We were told there were only two broken cranks in the last go around, my company had one of them, there was no plane crash, and no one was killed. I don't think that the statement that aircraft engines are lightly stressed because of the large displacement is exactly accurate. Recip stresses from high RPM are traded for combustion stresses from large bore cylinders trying to develope the power at lower RPM. This also makes the engine more prone to detonation. To produce the same horsepower, the slower turning engine has to produce much more torque which ups the mechanical loads as you well know. Have somebody show you a connecting rod out of an angle valve Lycoming engine. It looks adequate for a fuel dragster. They make it like that for a reason. A 150hp aircraft engine will weigh about 250 lbs ready to go. How about the North* with a cooling system.

dkozloski
04-26-05, 01:27 AM
Bbob, I'm mystified. The crank in a TIO-540 J2BD Lycoming 350HP engine is big and forged from near labratory grade steel. The rods are fully machined all over with tongue and groove cap joints and a cross section about three times that of any car. The piston pins are of the highest grade steel about twice the size of any car and is subjected to several special inspection procedures. If this engine is supposed to be so lightly stressed what the hell breaks this stuff? It's turning so slowly that recip loads compared to combustion loads are negligible. All in the interest of light weight. The limiting BMEP is about 180 PSI. I think there is more to this discussion that needs a pencil and a piece of paper put to it. Also I can't seem to locate a single example of an adapted auto engine that produces 300+ HP as it is presently installed and is certificated. The Thunder Mustang is 450HP but is a purpose built engine and not certificated. There was one other that started out as an adapted engine but morphed to a purpose built that is about 600HP but dormant now. {(update) Orenda engine is Kaput!} All the others that hit the headlines with a big flash have fizzled out when put to the test including Porsche. Could it be that the process is a hell of a lot harder than bolting a prop on a car engine for your puddle jumper. When I put a North* in my piper Navajo how much power am I going to see turning it 2700RPM like the engine it replaces? What kind of boost pressures am I going to see to get 350HP at 2700RPM like the engine it replaces? Maybe we better richen it up to keep the exhaust valves in it. Whoops! The specific fuel consumption just went out of sight. Now we can't carry enough fuel to be useful. At this level, how long will the engine last? Maybe we should scale up the North* a little to about 500 cubes. Now lets add the weight of the cooling system. Whoops! Now this thing is too heavy to get off the ground. Lets try adding a reduction gear to get the RPM's up instead. Whoops! it just broke from the gyroscopic propeller loads. I guess maybe this isn't as easy as I thought it was going to be.

dkozloski
04-26-05, 01:03 PM
Mechanix, I can't find where Buda ever made an aircraft engine but they did make a whole range of industrial gas and diesel engines that had a very good reputation. The smallest I ever saw was a four cylinder gas engine in a Keystone water well drilling rig and the largest was in a six cylinder diesel in a Northwest dragline. It looks like they were bought out by Allis-Chalmers in the 50's.

Stoneage_Caddy
04-26-05, 02:18 PM
I saw a 4.0 Aurora engine run at WOT for 10.5 days one time. It ran full throttle, max power, 6200 RPM for 252 hours in one stretch in a car. In the process it set 2 world land speed records (that still stand) and 42 other international and national speed records. I have a piston from that engine on a plaque on the wall in front of me. Looks fine to this day. Interesting statistic...during that run the car went a total of 48, 500 kilometers and the piston traveled 7000 miles...up and down the bore. Amazing , the rings are about 25% worn after scrubbing on the cylinder wall for 7000 miles.


I.
Thats the Aerotec with AJ Foyt driving right ?? Pretty neat car , overgorwn march indycar chassis if im not mistaken ...

Bbob , dokoz ..eveyone else ....why havent we seen any advances out of headgaskets ? Why not have .40+ cast "o rings" in the block to mate with the head at all water oil and combustion passages ? Seems like it would work fiarly well to me ....

As far as diesel being able to run to 5k ....i dunno , ive had a leaky detriot run away from me , seems like she barley made 1,000 rpm more than the limited rpm and stayed put till i could get the blower flap to shut to kill the engine ....the internals are so heavy that i think the limit is there just to keep it in its peak powerband ....i dont think they will even try to run in any kind of high powerband ...might see it in a turbocharged detorit 2 stroke but thats about all youd see a high rpm in

dkozloski
04-26-05, 02:31 PM
Back in the 50's a Cummins diesel led the Indy 500 for a substantial period of time. Update! In 1952, Cummins diesel led the race from the poll position. There have been many examples of aircraft diesel engines. Most were either too heavy or fragile.

Stoneage_Caddy
04-26-05, 02:56 PM
seems like the cummins car sucked some kind of rubber into the turbocharger cuaseing it to go out of the race .....saw that car a couple years ago at the museum , kinda neat how they got the engine layed over

aircraft engines at indy did much beatter ...till Lotus Cut the fuel pump shaft to cause it to fail ...or those pesky 3 dollar bearings LOL ...or when (was it usac then?) mandated some sort of air inlet specs.....

CTX-SLPR
04-26-05, 03:25 PM
Oy... I didn't want to get into this but I really feel drawn in. First off my job is an NDE inspector for Air Force aircraft, I get to see the failures as they come in, jets, props, structures.... you name it, I've probably had it through my lab.
On the subject of aircraft engine loads... its called a fatique life, the reason that aircraft engines are overhauled so often is that the parts are approaching the inspection points along thier fatique life. Like was pointed out earlier you can't just pull over in the sky when your engine decides to throw a rod out the side of the crankcase or gacks a gasket. To counter this you inspect the parts based on historical trends in part failure life so that you catch a crack at .010 or less lest it grow to the point of a "zipper" failure and the crack propigates across the entire part supersonically.
Any engine's power output can be judged by the amount of fuel it is consuming at that point, while every engine uses fuel at different rates per horsepower those differences are trival when compared to the difference if fuel needed to make even nominal differences in power. If you look at the accelerator position of an automobile engine at cruise you are only looking at less than 10% throttle position, on a carberated engine you are generally cruising in the idle circuits of the carb! This mean to propel the vehicle the engine is only producing 40-50hp to balance the areodynamic and friction loads on the driveline. The driveline is also directly coupled to the propulsion medium via the tires. In an aircraft or marine application the engines cruise at 75-85% max power, infact military aircraft are rated for near indefinate sustained cruise at "military power" esentually WOT at redline. Some piston aircraft have augmentors such as water injection or leaning the mixture out for more power but these measures are for burst capability only and drastically reduce the longevity of the engine. These power levels are required because the engine is indirectly coupled to the drive medium, be it air or water, by the propellor and the fact that the drag forces go up as a square of the velocity meaning to keep an aircraft sustained at 250mph, you are encountering 11x or more the aerodynamic resistance. As far as the operating environment, as air gets less dense the thermodynamic heat capacity of a specific volume of air goes down which make the cooling measures, be it liquid or air cooled, become less and less effecient so the engine environment is much harsher on the components.
In sumation in the lifespan of an aircraft engine the engine spends pretty much all of its time running at 80% or greater throttle, while an automobile engine spends maybe 10% of its life at those power levels unless its a racing application. While apples to apples comparison of engine power between rpms, the higher rpm power generation creates higher loads, power at low rpms has its own problems, which can be seen in engines like the Buick Turbo 6 which requires very tight tollerances to keep the oil in the bearings when making 400lb-ft at 2400rpm. Also lower rpm power requires much more aggressive anti detonation measures since the dwell time of the fuel-air mixture in the chamber means more opportunity for stagnation and hotspot preignition. Bbob, while I have respect for you as an engineer, I do believe that some of your theories and assumptions in this case are flawed though I cannot comment why they are flawed. I hope to contribute to this discussion.

Thanks,

Lt William Sanders
USAF Physicist

BeelzeBob
04-26-05, 03:26 PM
There are some major advances in head gaskets apparent in the market. The new Supercharged Northstar uses mulilayer steel head gaskets with a printed neoprene layer for liquid sealing. That type of gasket can handle some incredible loads and clamping pressures but it does require a very fine, ground surface finish on the deck faces and any scratches or other imperfections will hurt the microseal capabilities.

dkozloski
04-26-05, 03:32 PM
The Granatelli-Parnelli Jones deal with the Pratt & Whitney PT-6 was blamed on a bearing but the real problem was that the chassis was a "Flexible Flyer" and the resulting misalignments killed the bearing. USAC decided that since it didn't sound like a race car they would just strangle it with an inlet area rule that would rule out turbines. FWIW, if a gas turbine puts out 400 shaft horsepower, it is generating an additional 800 horsepower that is turning the compressor section. As a result a 400SHP gas turbine has to consume enough fuel and air to create 1200 horsepower. This translates to an efficiency of a little over 30% which is not too bad compared to a recip.

Stoneage_Caddy
04-26-05, 03:48 PM
Oy... I didn't want to get into this but I really feel drawn in. First off my job is an NDE inspector for Air Force aircraft, I get to see the failures as they come in, jets, props, structures.... you name it, I've probably had it through my lab.
On the subject of aircraft engine loads... its called a fatique life, the reason that aircraft engines are overhauled so often is that the parts are approaching the inspection points along thier fatique life. Like was pointed out earlier you can't just pull over in the sky when your engine decides to throw a rod out the side of the crankcase or gacks a gasket. To counter this you inspect the parts based on historical trends in part failure life so that you catch a crack at .010 or less lest it grow to the point of a "zipper" failure and the crack propigates across the entire part supersonically.
Any engine's power output can be judged by the amount of fuel it is consuming at that point, while every engine uses fuel at different rates per horsepower those differences are trival when compared to the difference if fuel needed to make even nominal differences in power. If you look at the accelerator position of an automobile engine at cruise you are only looking at less than 10% throttle position, on a carberated engine you are generally cruising in the idle circuits of the carb! This mean to propel the vehicle the engine is only producing 40-50hp to balance the areodynamic and friction loads on the driveline. The driveline is also directly coupled to the propulsion medium via the tires. In an aircraft or marine application the engines cruise at 75-85% max power, infact military aircraft are rated for near indefinate sustained cruise at "military power" esentually WOT at redline. Some piston aircraft have augmentors such as water injection or leaning the mixture out for more power but these measures are for burst capability only and drastically reduce the longevity of the engine. These power levels are required because the engine is indirectly coupled to the drive medium, be it air or water, by the propellor and the fact that the drag forces go up as a square of the velocity meaning to keep an aircraft sustained at 250mph, you are encountering 11x or more the aerodynamic resistance. As far as the operating environment, as air gets less dense the thermodynamic heat capacity of a specific volume of air goes down which make the cooling measures, be it liquid or air cooled, become less and less effecient so the engine environment is much harsher on the components.
In sumation in the lifespan of an aircraft engine the engine spends pretty much all of its time running at 80% or greater throttle, while an automobile engine spends maybe 10% of its life at those power levels unless its a racing application. While apples to apples comparison of engine power between rpms, the higher rpm power generation creates higher loads, power at low rpms has its own problems, which can be seen in engines like the Buick Turbo 6 which requires very tight tollerances to keep the oil in the bearings when making 400lb-ft at 2400rpm. Also lower rpm power requires much more aggressive anti detonation measures since the dwell time of the fuel-air mixture in the chamber means more opportunity for stagnation and hotspot preignition. Bbob, while I have respect for you as an engineer, I do believe that some of your theories and assumptions in this case are flawed though I cannot comment why they are flawed. I hope to contribute to this discussion.

Thanks,

Lt William Sanders
USAF Physicist
uh oh ..the boys from wright patt are here ....

last time i seen them was when my sargent submitted my idea for modifying the seatbelt on the MB4 Tow tractor (to keep it form getting destoryed by the door strikers)...my humble contribution to the nation ...LOL

Anyway ....im curious , you say that as the air gets thinner it wont cool as well ? so im guessing there is a limit to how much alititude you can carry on a aircooled aircraft engine ? or does the cooler high altitiude air compensate ?

probably off topic ...but curiosity ....i just love this thread ...ive turned into a engineer groupie

BeelzeBob
04-26-05, 03:59 PM
Lt...which ones are flawed..?? Be specific and it will not require such a long post to respond.

Keep in mind, some of my commments are a bit tonque-in-cheek. Like I said earlier, I think I can carry the argument of the "automotive engine in an airplane" either way. There would be no discussion here if I just agreed with dkozloski....so I took the other approach. I could just as easily argue the points you are making if necessary...LOL.

The engines you mentioned in your comments about military aircraft engines are all turbines, I take it..?? The piston aircraft engines in military applications were never rated for very long at maximum power settings...something like 200 to 300 hours if I remember reading correctly. A close friend of mine's father was a flight engineer on a Superfortress in WW2 and commented occasoinally about how carefull they were with those engines and how they never ran them for very long at take off power because of overheating, detonation and oil temperatures. And, if a Merlin or Allison use the nitrous for "full war emergency" power the engine was replace before the next hop if the reports that I have read are correct. So...the definition of what warrants as "full power" is open for discussion.

Turbines are a total different story for another day. They are not subjected to the same problems as reciprocating engines that this conversation started about.

Even if the piston engines are rated for operation at max power settings, my point is that the engines are torn down very frequently and rebuilt or recertified as new. If an auto engine were torn down as frequently and run per a prescribed duty cycle like an aircraft engine is run they would be just as efficient and just as reliable.

The engines are certainly designed for different uses. The torsional fatigue issues with the crank shaft swinging a prop are first and foremost. With the prop directly mounted to the crank an automotive engine would fail the crank very rapidly I would imagine due to the severe torsionals. The simple difference in appearance of the two cranks is evidence of this.

I have seen a Northstar mounted on a test stand with a custom Gerswinder 2:1 reduction drive swinging a variable pitch prop run for 300 hours at 4400 RPM and 80 percent power (roughly 85 kPa manifold pressure with a baro of 100 kPa) and the engine and drive looked absolutely perfect at teardown. Does this qualify the engine for aero use....no...it is not certified nor does it have the redundancies necessary but it does indicate that the engine has some capability to withstand that type of use. And that is running at a reasonably high specific power setting...not idling down the road. How would that relate to a TBO....who knows at this point. One has accumulated over 500 hours of flying with no problems so far so.....tick tick tick...LOL For a one off to be this successful the engine must have some degree of capabiliyt...it didn't explode at the end of the runway, anyway.

This whole thing came up with the implication that auto engines do not have to be as accountable for failures and the implication that they do not have to be as durable.

My point is that aero piston engines are pretty well understressed due to the large displacement that they employ and the lower RPM's governed by the direct mounted props for simplicity and cost reduction. The engines ARE beefy, I agree. As mentioned above, look at the differnce in the cranks and it is readily apparent that the aeroengines are designed for a different mission.

The other thing about piston aero engines that gets ignored is the fact that they loose significant power at higher altitude so , even though they are running WOT, they are not making the rated power unless they are turbo-normalized. This is far less stressful on the engine than running at the actual rated power.

There is no question why the aero engines have TBO's specified. Obviously it is hard to pull over when one breaks. My point is that they STILL blow up with some regularity even maintained like that. For the small number of them flying (relative to car engines) the failure rate is surprising.

Aero engines are designed for specific operating points and specific operating speeds. Many pilot hand books specify that the engine is not to be run at a certain specific RPM for more than a "time limit" due to prop torsional vibration issues. Think we could do that with a car engine...??

It truely is an apples to oranges comparison in my book....which is why I jump in when someone trys to make car engines look so poor by comparing them to aircraft engines. Piston aircraft engines are definitely run hard but they are also way overdesigned and coddled with low specific output and very specific operating parameters. Car engines have to do most everything, run at high RPM, pass emissions, get good fuel economy, etc.....

There is no reason in the world that most any car engine could be converted to an aero power unit IF given the correct resources and operating environment. The design would have to incorporate a redrive unit and/or the HP expectations would have to be reduced to accomodate the specific displacement of the engine so as to run it in the range of other aero engine specific outputs. The reliability is in the process control of the engine and the parts manufacturing. I think that the automotive engines of today are easily just as reliable as aircraft engines via the quality control of the components and assembly. Most any of the problems discussed on this forum are indicative of very long term operation....2 to 3 times the equivalent TBO of an aircraft engine....so these "issues" would have been addressed at an earlier TBO if treated like aircraft engines. Besides, in all the years posting on this board, I have only heard of one out and out failure of a Northstar engine that resulted in parts on the ground and the driver walking home....and the individual in question took the car onto the expressway to whip it to see what the noise in the engine was....LOL. The failures here have all been nuisance items...a head gasket leak would not crash the plane.


Anyway....it is an interesting discussion. Let's switch sides and see how each other does with the opposite debate....LOL.

BeelzeBob
04-26-05, 04:06 PM
Thats the Aerotec with AJ Foyt driving right ?? Pretty neat car , overgorwn march indycar chassis if im not mistaken ...




AJ Foyt drove the Aerotech in the late 80's and set the closed course record and the flying mile closed course records. The car is essentially an 85 March indy car chassis with the body shell hung on it. The engines used for the late 80's "testing" were replica-Quad 4 engines.

The Aerotech redux that I was referring to was done in the early 90's. The cars were completely redesigned and refitted with 4.0 Aurora production engines and they were set up for endurance running. The one car that set the world land speed records ran for 10.5 DAYS continuously at full throttle. It made a pit stop every 2 hours for fuel and tires and ran WOT at 175-190 MPH the rest of the time. AJ Foyt was nowhere around for this in December of 1992.

dkozloski
04-26-05, 04:08 PM
Turbo charged aircraft engines can be altitude limited by a lot of factors. The turbo can run away be cause of the low density intake air. The prop can run away because of the lack of bite with the thin air, the engine can overtemp from the lack of cooling from thin air. Which makes all the more remarkable the feat of the Italians in setting the absolute altitude record for piston aircraft with an altitude of 56,046Ft. using a turbocharged engine in the 1930's. The record still stands.

dkozloski
04-26-05, 04:18 PM
The latest data I have indicates that a pilot that flies piston engined aircraft exclusively can expect an engine failure requiring a shutdown every 5000 hrs. I personally have been flying my own aircraft since 1957 and have never had an engine failure or forced landing there from. This includes stuff like running out of gas. Figuring an average speed of 200 MPH this figures out to walking home every 1,000,000 miles. Bbob you auto guys have one hell of a long way to go to get your reliability up to this level.

Stoneage_Caddy
04-26-05, 04:22 PM
WOW .....56k in 1930......geez .....so there is indeed a limit ....

bbob , you have certainly had a career i would .....go to prision for .....

BeelzeBob
04-26-05, 04:24 PM
Bbob, I'm mystified. The crank in a TIO-540 J2BD Lycoming 350HP engine is big and forged from near labratory grade steel. The rods are fully machined all over with tongue and groove cap joints and a cross section about three times that of any car. The piston pins are of the highest grade steel about twice the size of any car and is subjected to several special inspection procedures. If this engine is supposed to be so lightly stressed what the hell breaks this stuff? It's turning so slowly that recip loads compared to combustion loads are negligible. All in the interest of light weight. The limiting BMEP is about 180 PSI. I think there is more to this discussion that needs a pencil and a piece of paper put to it. Also I can't seem to locate a single example of an adapted auto engine that produces 300+ HP as it is presently installed and is certificated. The Thunder Mustang is 450HP but is a purpose built engine and not certificated. There was one other that started out as an adapted engine but morphed to a purpose built that is about 600HP but dormant now. {(update) Orenda engine is Kaput!} All the others that hit the headlines with a big flash have fizzled out when put to the test including Porsche. Could it be that the process is a hell of a lot harder than bolting a prop on a car engine for your puddle jumper. When I put a North* in my piper Navajo how much power am I going to see turning it 2700RPM like the engine it replaces? What kind of boost pressures am I going to see to get 350HP at 2700RPM like the engine it replaces? Maybe we better richen it up to keep the exhaust valves in it. Whoops! The specific fuel consumption just went out of sight. Now we can't carry enough fuel to be useful. At this level, how long will the engine last? Maybe we should scale up the North* a little to about 500 cubes. Now lets add the weight of the cooling system. Whoops! Now this thing is too heavy to get off the ground. Lets try adding a reduction gear to get the RPM's up instead. Whoops! it just broke from the gyroscopic propeller loads. I guess maybe this isn't as easy as I thought it was going to be.


Not sure what broke it. I understand that it was a fatigue crack propagating from a forging flaw that was exacerbated by the prop harmonics. The report that I read indicated fatalities were involved but I did not research it thoroughly.

You could put the Northstar engine in there if you were satisfied with 170 HP at max output...that would put it on par with the specific output of the Lycoming engine. The apples to oranges comparison is that people compare the same HP engines in cars and aeroplanes. They are NOT rated the same. A passenger car engine is rated for "burst" use (no pun...intended or other wise) such as the operator would experience in a burst of power. They are NOT rated for continuous operation at that power setting like an aero engine is. I would be the first to admit and acknowlege this. Rate the car engine the same way as the aircraft engine and the componetry is perfectly capable of meeting the same duty cycle.

How do you think aero engines get away with such severe leaning requirements? They run very low specific output.

Yes, they are large displacement, large bore engines prone to detonation...that is why they need 101 octane leaded fuel. Wish we could get auto fuel regulated half as good as aero fuel is regulated. Emissions could be cut in half again if that were the case.

I realize that air craft engines are run hard but I also realize (and this is my point) they they are relatively understressed due to the specific output of the engine, they get special well regulated fuel, they have relatively short lives with distinct TBO's and they are run at a specific, designed speed under a very specific operating regime. Car engines have the luxury of none of that and yet they are very durable and reliable. Hard to believe that a car engine couldn't fly an airplane given a chance.

The Orenda is an interesting case. They had no case from the beginning but didn't realize it. They were trying to get WAY too much power from WAY too small of an engine. I met with one of the engineers that was consulting with Orenda back in the mid 90's. He had read a cooling paper that I wrote and wanted to talk. Out of that discussion came the dual water pumps that they employed that finally allowed them to at least pass their durability testing. They had WAY too little cooling flow to eliminate the themal gradients in the engine. I think that the chances of every engine passing that test were slim to none, though. They were just trying to make way too much power. They were actually turbocharging, not turbo-normalizing so they were really stressing the engine.

The Thunder Mustang....funny...I talked, at length, with one of my colleagues, with the guys that build that motor...Team 6 or something like that. They have killed a couple of guys. One of their problems is they are running hydraulic lifters in the motors which do not like the air injested by the oil pump during aerobatic maneuvers....so they drop valves due to the lash created. The also have a corrosion problem with valve stems. Many of the guys run the engines with short stacks so when they shut down the exhaust valves see humid air and corrode outside the guide if they are being held open. This rust then eats up the valveguide and sticks the valve. They have since gone to solid lifters and inconel valves I understand and are having no more problems with engine failures but that is just heresay.


There is no question that the engines are designed for different missions. As an example, see my post, how effective would an aerocraft engine be if transplanted into a car....

Stoneage_Caddy
04-26-05, 04:26 PM
wait ...didnt the mazda 13b get certified for aircraft use ?

BeelzeBob
04-26-05, 04:34 PM
LOL LOL

We can keep flinging these apples and oranges out there forever....

200 MPH....most piston engine private aircraft do not average that speed...do they, now??

Still....5000 hours, if a car engine blew up every 5000 hours it would be hell to pay. You can't really count the miles on the air plane as it is a completely different operating condition with no speed limits or roads to stick to. The most accurate and realistic comparison is hours of operation....besides, that suits MY argument the best. Next time, I get to pick your side of the arguement.

Realize also, that I collaborated on writing an article that was in the Smithsonian Air and Space magazine several years ago entitled "Why car engines don't fly" and provided the data and information on the "car" engines and the parts and pictures. Don Sherman wrote the article. I supplied the parts and pictures for the Northstar engine pieces used as an example in the article....so there IS another side to this argument. Funny thing is, he started out writing the article about how automotive engines could be used for aero power...and ended up changing his mind.

dkozloski
04-26-05, 04:38 PM
The Tucker automobile had a Franklin engine produce by Air Cooled Motors. Franklin was not reknowned as a long lived aircraft engine with major overhauls every 600 hours and a ring and valve job every 300 hours according to the manuals. The cylinders were one piece aluminum castings with shrunk in cast iron liners that were soft as butter. Even at that they attracted a following. Modern engines have two piece cylinders with steel cylinder barrels and a screwed and a shrunk on aluminum head. One oddity is the Teledyne Tiara that uses separate cylinder heads held on by long through bolts. The prop is driven off the camshaft rather than the crank which gives an effective 2:1 reduction gear. As far as I know, if there are any of these still running they are in Agplanes.

Stoneage_Caddy
04-26-05, 04:42 PM
Still....5000 hours, if a car engine blew up every 5000 hours it would be hell to pay. You can't really count the miles on the air plane as it is a completely different operating condition with no speed limits or roads to stick to. The most accurate and realistic comparison is hours of operation....besides, that suits MY argument the best. Next time, I get to pick your side of the arguement.

.
sorry to keep butting in ...my last question i swear ....

You say that the aircraft engine sees a diffrent use ....

i read the other day that most mechanical failures occur when something is chnaging states , ie accelerateing or declerateing ....wouldnt this mean that a engine that has to contantly change states would be more prone to failure ?say for insatnce a 305 chevy in a new yourk taxicab (many stop lights running from 650 rpm to maybe 4k every couple minutes)? Vs a cessna that runs from ancoridge to fairbanks every day (idle,"wot" idle once a day )?

dkozloski
04-26-05, 04:51 PM
Bbob, I chose 200MPH because I had in mind the Navajo Chieftans of which we still have seven of in our fleet and use the Lycoming TIO-540 J2BD engine. The one we had that failed was reported as an "engine feathered in flight" incident and the plane proceeded to destination. I don't know the details of any other. Stoneage Caddy, I saw a 13B Mazda in a Super Cub but it was never certificated and the fuel consumption was so high you couldn't get out of sight of the airport. The owner gave up and put the old engine back in it. FWIW, a rule of thumb is that most engine failures occur at the first power reduction after takeoff.

dkozloski
04-26-05, 05:55 PM
Bbob, I still think you are minimizing the stresses in aircraft vs. auto engines. If you are turning the auto 6000RPM and the aircraft is turning 2700RPM you are going to have to produce 2.22 times the torque to get the same horsepower. This will more than double the bearing loads from the combustion forces. Internal parts will have to be reinforced to withstand these forces so the recip loads go up but of course not exponentially as they do with increased RPM. I think it would be close to a wash. The loads and stresses that loosened up all the main bearing inserts and galled the big end bores of rods had to come from some where. All the case half shifting and fretting I have seen didn't happen for no reason.

BeelzeBob
04-27-05, 12:21 AM
OK OK OK I give up...LOL.

Like I said, I entered into that arguement somewhat tongue in cheek because I still say that airplane engines are coddled more than auto engines and that auto engines are more reliable in the service that they were designed for.

As you pointed out, the aircraft piston engines are build very robustly with HUGE crank journals, large rods and huge bearing areas, etc. Certainly they handle a lot of torque...I realize that. My point is that they do not live nearly as many hours before they are at TBO and torn down and remanufactured. If car engines were forced to be torn down like that none of the problems we read about on here would ever happen.

Despite the very low volume, heavily overdesigned nature, huge expense, carefull quality control, etc. the aircraft engines still suffer major failures fairly frequently. An engine failure every 5000 hours is a lot for a car. The problems on here rarely if ever are a walkhome and certainly supply lots of warning. MOst of them are, quite frankly, an inconvenience at very high miles.

I am the first to admit that comparing auto engines to aircraft engines is a very difficult thing to do. But, there is simply no reason that an auto engine couldn't work just as reliably in an aircraft if it was treated the same way...i.e...run at the same specific power for the displacement and run at the same RPS's etc. The quality control of the auto engines is better, in my opinion, than aircraft engines given the hours/miles the car engines cover and the number of them on the road. Very very few ever result in a catostrophic engine failure yet engine failures on airplane engines are relatively common considering the low number of them and the low hours they operate and the rate that they are checked and overhauled.

The fact that many of the aircraft engines have changed little in the last 30 years indicates that they are way behind in the material and engine design technology. Heck, most of them have carburetors and fixed spark timing...

I have often argued this point with homebuilders that want to use auto power in an airplane. They totally misinterpret what the engines are capable of and simply see the HP rating of the engine. They refuse to understand that the engines are rated differently and think that they can treat an engine that makes over 1 HP per cubic inch the same way that they can treat an application specific aero engine that makes only .5 Hp per cubic inch. BIG BIG difference....even if it is making more torque due to the lower RPM...it is made to run at that RPM and is still very low specific power.

So....I want to argue the side that says that auto engines cannot fly....LOL....that is an easier task and is what I really believe.

JimHare
04-27-05, 12:44 AM
Besides, argue the point as much as you want but a car engine does a hell of a lot better job in an airplane than and airplane engine does in a CAR....LOL....I have NEVER seen one of those running around...but I have seen a LOT of car engines flying in airplanes.

As perhaps the most uneducated watcher of this thread, I thought I'd toss this in here - I remember reading a piece in a car mag back in the early-mid 70s about a Ferrari owner in England behing overwhelmed one day by a R/R blowing by him like he was standing still. Ferrari owner calls R/R factory, wants to know about this barely-subsonic R/R they have. They claim no knowledge. Ferrari owner digs around more. Turns out R/R is owned by ex RAF pilot or mechanic and he shoehorned a Merlin or something like that into his Silver Cloud.

Don't know if it's true or not, has anyone else ever heard this story? :)

EDIT: Sunuvagun, look what I just found.. LOL

http://www.theminifarm.com/john_dodd.htm

Stoneage_Caddy
04-27-05, 01:17 AM
Ive worked on a Cloud 2 ...there wasnt much more room in there...let alone for a merlin those are firggin huge comapred to the box stock alum v8 i found cowering in there ....

sounds a bit like the 67 Impala with JATO rockets strapped to the roof that were found in a junkyard story...

One story i know of thats interesting was in the early 90s ....At the time at indy there was alot fo talk that the buick just didnt have what it took to run the full 500 miles (it really didnt) ..I cant remeber for sure whose car it went into but a Buick V6 Indy engine was transplanted into the drivers personal GN and he drove the GN to and fromt he track for the month of may to prove the Indy v6 would make 500 miles ...I think it was Scott Brayton but imnot sure ....
Im not sure how real this was ....at the time they were running "Stock block" engines but ....how a menthaol burning Buick V6 was put into a GN and somehow ran still making the 40+psi of boost it made in the indy car without liqufying the rest of the powertrain is beyond me ...and all the electronics that would have to me modififed ...and the hood of the buick wouldnt be able to be closed ...or coaxing a "Pop off valve" out of USACs hands to toss in a street buick for personal use .....all sounded fishy to me ....but i do remeber hearing the story ....even "the buzzard" (the indy classic rock station) repoerted it .....

also at the time the engines were stressed members of the monocoge (sp?)(still are) so even then i wonder if it would bolt up to a what 700r4 ?

Stoneage_Caddy
04-27-05, 01:20 AM
by the way jim im the most uneducated one here ....and im too damned young to boot ...but man am i leanring lots from you guys

dkozloski
04-27-05, 02:54 AM
Bbob, I agree with most of what you have to say. My take on the aircraft recip engine failure rate though is that it has more to do with the fact that the engines are very easily heat saturated and people try to operate them as if they were water cooled auto engines. An example would be a slow high power steep climb out that runs engine temps to the redline followed by a dive to the airfield at the destination that results in shock cooling. I had customers that when I tore down their engines at overhaul they looked like new inside. For them I could fill out the paperwork that gave them extended overhaul intervals. Others loked like they could tear up a cannonball. I am reminded of a quote from a Pratt & Whitney manual that stated that there were only so many ups and downs in the pistons and you could get them all out at once or over an extended peoiod of time. I agree that an auto engine is much more robust and forgiving device. Too bad they don't seem to work out in real airplanes. Now if you could only remotely approach the reliability and longevity of an aircraft turbine engine with your auto engines you would really have something to crow about.

dkozloski
04-27-05, 04:34 AM
Bbob, you mentioned a friends dad that flew in Superfortresses. That aircraft had Curtis-Wright R-3350 engines that were put into service 60 years ago under emergency wartime conditions with the same TBO as the Gnome rotary in WWI. The big problem with this installation was that it had a separate exhaust stack for each cylinder that was attached to the cowling rather than the engine with a flexible joint in between. The joints would fail under high power settings and set the plane on fire but this was no fault of the engine. When this engine was further developed it was 3350 cu.in, produced 3500 REAL SAE HP for takeoff, the crankcase was a steel forging, the cylinder heads were fully machined aluminum forgings,(I made one of those into a lamp), it had fuel injection like a diesel direct to the combustion chambers, low tension ignition with a separate coil for each spark plug, two-stage two speed geared superchargers, and exhaust driven turbines that returned power directly to the crankshaft through gearing. It had a specific fuel consumption of 0.32lbs/BHP/Hr. and a TBO of 2500hours. The flight engineer had an ignition scope and a direct reading torquemeter to monitor the performance of the engine in real time. Since the DC-7 aircraft involved had a cruising speed over 300MPH this figures out to over 750,000 miles between overhauls. You'd have to have a truckload of North*'s to equal just one of those beasts..

Maxoom
04-27-05, 11:12 AM
dkozloski - interesting comment about how failures happen most often when you pull back on the throttle after take-off. I can relate ...

Most of my engine experience is with high-performance outboards. You're most at risk for meltdown while coming off the throttle after a high-speed pass. 2-strokes enjoy a slight boost in volumetric efficiency with a slightly over-rich mixture, so that's how most are set to run. However, if you want that last mph on top or that last .01 ET you've got to lean it out right to the hairy edge. Then, anything that upsets the mixture, such as suddenly chopping the throttle, is a recipe for disaster.

Some engines are more susceptible than others. For example, if you insist on running carbs on a highly modified OMC big block looper, you'd better have some way to momentarily richen the mixture as you back off the throttle. Fuel injection is the answer, but it's beyond the means of most of the good ole boys around here.

I'm still puzzled by the N* headbolt thread failures. I've pulled down many an outboard over the years. Even in the presence of saltwater, stuck bolts and damaged threads in the block are the exception rather than the rule.

dkozloski
04-27-05, 12:12 PM
Maxoom, my two stroke experience is similar to yours. With the 250CC Yamaha twin road racers, if you ran out of gas the engine would seize before you could get the clutch pulled in. As far as outboards go; my neighbor had a Mark 55H Mercury Quincy loop engine that was 45 Cu.in. and put out 135HP on gas back in the early 60's. The noise from the exhaust was stupifying. I designed and built a transaxle package that had two Mark 650 Mercurys geared together with a Muncie four-speed transmission between them that connected to a Halibrand quick change rear end that I was going to install in a Ford GT 40 replica. That project ended when it went under water in a big flood in 1967. I still have the Mercurys and the quick change in my junk pile.

CTX-SLPR
04-27-05, 12:36 PM
I think the pulled head bolt threads are caused by casting porosity, I don't know if the Northstar is cast upside down or right side up but if the decks are some of the last things to be filled, you can get trapped gasses in the die that displace metal causing the area to be weaker. I'd acutally like to run a penetrant inspection of one of the decks of a block with pulled head bolts if anyone in Dayton has a spent one.
Oh and Bbob, I was talking about piston engines not turbines for military power. The V12 Merlin the Allison engines uses in WWII aircraft used water injection to cool the cylinder down enough to prevent detonation from running an overly lean mixture for emergency burst power, this power was not to be used very often or for very long but was factored into the life cycle of the engine if it did not exceed a specific useage amount.
I wonder what the failure rate was on those Teledyne Tiara engines with the cam driven props? It would seem with a smaller bearing diameter and much greater lobe to shaft overlap it would more resistant the vibrational harmonics of the prop, though I bet it played hell with the timing and valve lash. How many thrust bearing surfaces would a system like that have?

dkozloski
04-27-05, 01:14 PM
CTX-slpr, a more accurate description of the Tiara would be to say that the cam was driven by the prop reduction gear. The spur gear reduction gearing incorporated a flexible coupling that was called a vibratory torque control to address the torsional harmonics. The cam drive was never an issue. When the engine first went into service in Piper Pawnee Ag aircraft, there were a rash of failures that were thought to be centered in the torque control area and some changes were made with little effect. There were a lot of red faces when it was found that the actual problem was an oil passage in the crankcase that wasn't getting properly drilled on the production line. The Tiara was supposed to be the leadoff of a new generation of high tech engines but it never went beyond Ag use. Mid-Valley Aviation in Los Banos, California did a lot of the developement liaison for Teledyne Continental on this project.

dkozloski
04-27-05, 01:22 PM
Whenever I encountered pulled threads in an aircraft engine fastener that looked like the aluminum had crumbled, the feeling I had was that it was not a porosity issue but rather a corrosion issue. Careful examination of the crumbs would show evidence of corrosion products and quite often the area would have been subject to exhaust gasses. Of course it was hard to say what came first, the pulled threads or the corrosion.

BeelzeBob
04-27-05, 02:11 PM
The Northstar block is a diecast piece. The die is like a huge steel chinese puzzle with different slides, steel inserts and mandrels that form all the surfaces and passages. The die is assembled with the premachined cast iron cylinder liners on the cylinder mandrels and the molten aluminum is injected at very high pressures (like in the 20K to 30K PSI range) into the void created by the die sections. The aluminum chills and solidifies, the die is parted and the aluminum block is removed with the cylinder liners cast in place. The block cavity is positioned so that the block is sitting on end with the front of the block upwards.

The die fills so fast when the aluminum is shot into the cavity that it is really hard to describe just how it fills. There are numerous channels and fill ports to feed the molten aluminum into the die uniformly. This area of the process is heavily modeled to understand and control the diecast process.

In any aluminum diecast part this large (or any diecast part period....) porosity is a fact of life. Most metalurgists describe diecastings as porosity surrounded by aluminum..... The simple fact is that the aluminum fills the die very rapidly and skins over all the surfaces of the die as the die sucks heat out of the aluminum very rapidly and chills and solidifies the aluminum. As the interior of all the walls and solid sections solidify the aluminum cools and shrinks as it solidifies. That is where the porosity comes from. It happens. Porosity is controlled by making sections as uniform as possible, controlling section thickness, controlling the fill points, the die temperature, the shot speeds and pressures, etc. People make a career out of this so it is very complex.

Given this overview of the diecasting process it is impossible to say that there is no porosity in the casting to affect thread quality, strength, etc. I will say that critical areas of the block are routinely sectioned and inspected for porosity evaluation and the process controls on the casting process are myriad and detailed to ascertain that the level of casting quality is maintained.

It is certainly possible for a threaded hole to have some level of porosity in the material of that area. The thread design, thread engagement, etc. allows for this as it is understood as an inescapable part of the process. I wouldn't say that just because the threaded area has some visible porosity that that would be the reason for the threads failing.

I suspect that there are many different factors involved, honestly. If a head bolt thread does fail (or pull out...) causing a head gasket to leak it could be attributed to any number of possible causes, porosity included. I think that many head gaskets are damaged due to corrosion with the cooling system maintenance (or lack thereof) and then the head bolt threads are damaged removing the head bolts due to corrosion at the thread interface (the galvanic effect mentioned many times before) or the threads are damaged during cleaning by using a cutting tap or similiar procedure. It is hard to just state "A" reason that head gaskets or head bolt threads fail and I think that any attempt to lump all them under one single failure mode is inaccurate.

dkozloski
04-27-05, 02:29 PM
Teledyne Continental engines have been grouped into two categories for years; sand cast and Permold. Most of the problems with the sand cast engines center around changes in vendors and the Permold engines were subject to cracking. Years ago Boeing Aircraft decided to try to get a handle on outside suppliers by buying them up. They bought the aircraft brake division of Goodyear because they were the best in the world, at the time, in magnesium castings. They bought the company that had been suppplying Continentals aluminum crankcases for 30 years, made them an in-house operation and cut off all the old customers. It took years for Continental to recover from the loss of their supplier. I was told by their engineering people that their scrap rate for crankcases at times approached 50% due to a whole range of defects that would be found during the machining processes. As a result, the cost of a new crankcase can be in to $7-10,000 range. The production of aluminum castings is a black art with much of the techniqe centered around empirical data and the inspection of chicken entrails. As an aside, during the same time frame, Lycoming was having casting and crankcase problems that were at least as severe as Continentals but since their engines weren't getting sold to lawyers and doctors they never felt the same degree of heat over it.

Stoneage_Caddy
04-27-05, 02:37 PM
Teledyne ...must be the same Teledyne that made our P-23 Firetrucks ....Speaking of casting issues LOL....Trucks were 8 wheel drive with fully indepentent suspension , pretty advanced for 1994 .....USAF wanted Centrail Tire Inflation ..insated of desginign a new knkucle assembly they simply drilled into the stock knucles and hubs to insatll passages for the air to the tire ......caused cracking issues ...a couple of the 47,000 lb trucks lost entire wheel assemblys ....which caused the airforce to order weekly insepctions of the hubs and knuckles and limited the speed ont hem to something like 20mph ....

Some blamed it on castings , others blamed it on the Central Tire Inflation setup ....one day someone will tell me what really happend ...at any rate the airforce last i heard is repalceing the trucks with something from Colet

dkozloski
04-27-05, 02:42 PM
Stoneage_Caddy, the Army's new Stryker armored vehicles have the same central tire inflation system but I haven't heard of any wheels falling off. There is a whole herd of those things at Ft. Wainwright.

Stoneage_Caddy
04-27-05, 02:47 PM
I seperated just before wainright got there strikers ....ive really wanted to get a good look at those .....

the wheels coming off the 23 story was probably not well know outside my career field ....superising ....esp when you see it :
http://www.capecodfd.com/Pics%20Appar/Pic%20OT%20F403b.jpg

CTX-SLPR
04-27-05, 02:54 PM
I'm watching the same issue with turbine blades, they drill cooling passages whereever they want and then the cracks start growing because they decided to put a hole in a stress load location. Generally putting a whole in something load bearing is a terrible idea unless you design for the lack of material in that location. Aluminum casting is a black art, I hate inspecting castings as they are just a mess of porousity and voids and such, one of the best things to happen to casting is realitization that its not steel or iron and you have to heat the fool out of the casting die to keep from getting thermal stress risers from the molten aluminum contracting as it cools when it contacts the die.
Are you thinking the head bolts fail due to accelerated stress corrosion cracking out of the thread roots? Most of the head bolts on a Northstar are wet aren't they?

dkozloski
04-27-05, 03:01 PM
North* headbolts are in a well that is purposely kept dry although there are a lot of reports after failures that the wells are full of black liquid coolant. Once again, what came first, the coolant or the failure.

Stoneage_Caddy
04-27-05, 03:07 PM
I hope your not asking me ....I honestly dont know nuthin ....

Not to rattle Bbob or anything ...but for a simpleton like me after reading this thread i still wonder how those bolts are acting with the aluminum block .....aluminum and steel expand diffrent and all ...i mean thats why pistons are egg shaped right ? so if steel and alumiun are together i still dont understand how they could expand and contract in the area where the bolt threads mate with the alumiun threads in the block...when they put inserts in i can see it easier ....but i dont get how it works with a chunk of steel in a chunk of alumiun ..should there be a thrid "mediator" type material in there so brigde the diffrence in expansion beateen alum and steel ?

but it sure wouldnt be cost effective .....

maybe im missing something ...maybe the threads for northstar headbolts are of a diffrent desgin from any other bolt ...like pitch wise or something ....i know the length is special to comabt the overall expansion of the alumiun block being held in bythe steel bolt but where they acutally "mate" down there is where i wonder ...

i personnaly dont like studs ....why not a long bolt with a nut attched to the other end that fits into a hex shaped notch insde the block ....youd slide the bolt in the same manner as a head bolt but its be attched with a nut insated of the block isteslf ...or would the head walk around on the block deck as the engine ran?

i dont mean to doubt the engine or engineer(s), like i said i dont know nuthin ....thats why i ask so many questions ....sincerly interested

BeelzeBob
04-27-05, 05:22 PM
Don't loose sight of the fact that there are an awful lot of Northstar head bolts screwed into aluminum threads that do just fine for hundreds of thousands of miles.... There is nothing inherently wrong with steel bolts in aluminum threaded holes. They are used in millions of millions of engines. The main concern with threaded holes in aluminum is the inherent "weakness" of the aluminum compared to steel or cast iron. The joint typically is designed for 2 diameters of thread engagement in the aluminum part...i.e..if it is a 12 mm bolt then you need a minimum of 24 mm of thread engagement in the aluminum. Northstar headbolts are designed for about 2.5 to 3 diameters of thread engagement. There are concerns such as corrosion and the galvanic corrosion that can take place in the presences of an electrolyte...which is why the head bolt holes are purposefully dry and sealed off.

Every time I have ever taken a steel bolt out of an aluminum hole whether it be on a kart engine, motorcycle engine, lawnmower engine, snowmobile engine, car engine, Northstar, you name it the bolt ALWAYS cracks loose taking alot of force to overcome the inherent slight bonding at the interface of the threads caused by some low level of corrosion in the long term. It is very common so that is not the failure mode as has been postulated many times.

BeelzeBob
04-27-05, 05:29 PM
dkoz...not to belabor the aircraft thing and Lycoming but I did find a reference to the crank failures.

The article I found, interestingly enough, was in the latest issue of Flying Magazine. They indicate that 24 cranks failed in engines in airplanes while flying and that the failures resulted in 12 deaths and the recall/inspection of hundreds of engines. That is a lot more serious than even the article I remembered reading.

Since I am sure that the crank was designed for the application and certainly was pretty beefy I would be willing to bet on a quality control problem. That is the type of thing that I was referencing comparing car engine quality/reliability/dependability to piston aircraft engines. On a percentage basis if you assume that the Lycoming crank was designed for its mission and the Northstar crank is designed for its mission there would be Northstars on the side of the road everywhere with broken cranks. That is why I said that car engines have much better QRD on a percentage basis. Regardless of how the engines are run and the duty cycle that can be equalized by assuming that they are both designed for the task at hand. So, there would be no excuse for a crank failure, especially this number in a limited volume of engines. If GM's quality was that bad that cranks were breaking we wouldn't even be around today. Come to think of it.....I do not ever recall seeing a Northstar crank break ever.....ever....

dkozloski
04-27-05, 06:07 PM
Bbob, you are probably right in the numbers when you look at the overall picture. There was actually more than one seige of broken cranks. I was referring to the series that involved us and our failure. As far as I know the whole thing started years ago with some breaks showing up in aerobatic exhibition aircraft with crankshaft extensions that multiplied the gyscopic stresses. These were recalled and some process changes were made involving production. Next a new bunch of broken cranks appeared that precipitated another more widespread recall and some more production changes. While this recall and replacement was in progress one of the cranks that we had installed persuant to this recall broke and the whole fiasco started again. It didn't look like a quality control problem per se, as much as engineering choosing a defective production process. Everything we had has been repaired and the dust has settled again. During this period of time Lycoming hired Continental to do the recall repair work for them. This would be like Cadillac hiring Lincoln to pull their chestnuts out of the fire.
You might want to check with your friends over at the Chevrolet special engine plant. They had a seige of broken forged cranks that got so bad that the NASCAR engine assemblers I was familiar with said they had a 90% rejection rate of new cranks trying to find some they could use. It centered around the procedure of forging the cranks flat like a coathanger and then heating and twisting the crank through the mains to get the 90deg offsets required. It was resulting in broken cranks with the focal point of the crack originating below the surface. Granted, this was twenty years ago. I almost forgot, ask John Menard about broken cranks in V6 Buicks.

Stoneage_Caddy
04-27-05, 06:37 PM
Don't loose sight of the fact that there are an awful lot of Northstar head bolts screwed into aluminum threads that do just fine for hundreds of thousands of miles.... There is nothing inherently wrong with steel bolts in aluminum threaded holes. They are used in millions of millions of engines. The main concern with threaded holes in aluminum is the inherent "weakness" of the aluminum compared to steel or cast iron. The joint typically is designed for 2 diameters of thread engagement in the aluminum part...i.e..if it is a 12 mm bolt then you need a minimum of 24 mm of thread engagement in the aluminum. Northstar headbolts are designed for about 2.5 to 3 diameters of thread engagement. There are concerns such as corrosion and the galvanic corrosion that can take place in the presences of an electrolyte...which is why the head bolt holes are purposefully dry and sealed off.

Every time I have ever taken a steel bolt out of an aluminum hole whether it be on a kart engine, motorcycle engine, lawnmower engine, snowmobile engine, car engine, Northstar, you name it the bolt ALWAYS cracks loose taking alot of force to overcome the inherent slight bonding at the interface of the threads caused by some low level of corrosion in the long term. It is very common so that is not the failure mode as has been postulated many times.

sorry bob i didnt mean to imply it was a "problem" ....i personally cruise alot fo car lots ...im always looking at cadillacs just for fun .even mechanics specials(keeping eyes peeled for another project) ..ive seen some serious mileage on those northstars ...but i see more 4.9s with obscene aomnts of mileage ....

I know exactly what you mean about removing bolts from aluminum...for years ive come to know that "big force" then a "pop" on a bolt that sometimes only required 25lb ft to install ...a few times ive found myself eyeballing a 3/4 drive breaker bar for a 10mm bolt....

To be honest i wasnt nessearily going after the northstar and pulled bolts but just bolts into alumin period ...ive become quite proficent at "helicoil" and all that ...perhaps some pent up frustration ....ive just always thought that was why so many have given me greif (bolts into aluminum i mean)

There isnt much more im afird of when working on stuff than aluminum ....well maybe those damned phillips head screws .....wait till i find who is behind that one !!!!!

dkozloski
04-27-05, 06:49 PM
Lycoming recently lost a 96 million dollar lawsuit with their vendor that supplied the crankshaft forgings. Lycoming claimed there was a faulty heat treatment process by the vendor and the vendor claimed it was a bad design and a poorly chosen steel alloy. The vendor won the suit and collected over 80 million dollars in punitive damages from Lycoming. The blame has been laid at the feet of Lycoming engineering as of 3-11-05.

dkozloski
04-27-05, 07:28 PM
Crankshaft design seems to me to be a very interesting exercise. Once you decide on a bore diameter and center to center distance on the cylinders you have determined what the length of the crank is going to be and how much length you have to divide up between bearing widths and cheek thickness. Years ago, Continental decided their six cylinder cranks had marginal strength if they were going to increase engine output. Because they didn't want to increase the overall length of the engine they decided to narrow the connecting rods and rod bearings and increase the thickness of the crank cheeks. Because they did this in midstream you see identical engine models with both crank setups. Later Continental fell into the same trap that was to get Lycoming and had a spate of broken cranks and vendor and alloy changes before it was cured.

BeelzeBob
04-27-05, 11:05 PM
sorry bob i didnt mean to imply it was a "problem" ....i personally cruise alot fo car lots ...im always looking at cadillacs just for fun .even mechanics specials(keeping eyes peeled for another project) ..ive seen some serious mileage on those northstars ...but i see more 4.9s with obscene aomnts of mileage ....

I know exactly what you mean about removing bolts from aluminum...for years ive come to know that "big force" then a "pop" on a bolt that sometimes only required 25lb ft to install ...a few times ive found myself eyeballing a 3/4 drive breaker bar for a 10mm bolt....

To be honest i wasnt nessearily going after the northstar and pulled bolts but just bolts into alumin period ...ive become quite proficent at "helicoil" and all that ...perhaps some pent up frustration ....ive just always thought that was why so many have given me greif (bolts into aluminum i mean)

There isnt much more im afird of when working on stuff than aluminum ....well maybe those damned phillips head screws .....wait till i find who is behind that one !!!!!

Phillips head screws......yea.....don't even touch them with a screwdriver....go get the impact driver to knock them loose. You usually only get one shot. Then the philips head rounds out. Then you slot the head with a cutoff wheel and a die grinder and use the straight bit in the impact driver. Then you curse and start grinding the head off....LOL Been there, done that.

Stoneage_Caddy
04-27-05, 11:09 PM
Phillips head screws......yea.....don't even touch them with a screwdriver....go get the impact driver to knock them loose. You usually only get one shot. Then the philips head rounds out. Then you slot the head with a cutoff wheel and a die grinder and use the straight bit in the impact driver. Then you curse and start grinding the head off....LOL Been there, done that.
thats one fastener that has no buiness being in anything besides wood ...and even then thats debateable .....

however i have become a HUGE fan of the "Torx" !!! (after i bought a compete set)

dkozloski
04-28-05, 12:45 AM
An old mechanics trick; dip your Phillips bit in a container of coarse, grease mix, valve grinding compound before applying it to the screw and it won't slip. Also buy your bits by the handful and throw away the worn ones. My dad always told me not to blame my tools for something I couldn't do. You also might want to double check that you really are dealing with Phillips head srews and not Parker-Kalon or Reed & Prince.

Spyder
04-28-05, 02:45 AM
... ...Parker-Kalon and Reed & Prince? gonna have to look that one up one of these days...

mechanix
04-28-05, 11:27 AM
Parker-Kalon? I must admit I've never heard of that one. You are showing your age Koz! *lol* While exhuming past follies, let us not forget the cursed "clutch-head" screw. A brilliant idea, that one! *lol* It came and went faster than a J-Lo marriage! *lmao*

dkozloski
04-28-05, 11:58 AM
For years clutch-head was the screw of choice for GM door hardware. I still have a set of bits somewhere. As for Parker-Kalon, surely you have heard of P-K screws. Those are the bits that show up in a recently purchased assortment that don't seem to fit anything really well. They are probably to blame for the largest share of torn up Phillips heads. The strangest I have encountered is the five spline security Torx bits that you have to have a federal license to own because they are used in the federal prison system for door hinge and lock screws but Deutz Diesel uses them to hold the timing belt cover on.

dkozloski
04-28-05, 01:44 PM
More "Snerd's Words for the Birds". If you are having trouble with "stiction" of fasteners screwed into aluminum there are a couple of products that address this problem directly. Whenever I inspected a shop to see if I wanted them to be doing some sub work for me the first thing I looked for was what they were using to lubricate fastners, fuel fittings, and hydraulic fittings that were screwed into aluminum. Fleet Industries has produced a line of lubricants for the aviation field for at least 75 years that are the "gold standard". "Threadlube" is for steel to aluminum and aluminum to aluminum. I have used it for thousands if not tens of thousands of fasteners in aluminum and it works to prevent pulled and damaged threads both during assembly and removal. "Sealube" works for hydraulic and fuel fittings. The ultimate in anti-seize is produced by Go-Jo, the same company that produces hand cleaner. It is non-corrosive and even works with stainless steel fasteners used in turbine engines which is the toughest test I know. It looks to me to be a mixture of EOS and atomized zinc powder. Because these are specialized products you may have trouble finding them but you might start at www.AircraftSpruce.com (http://www.AircraftSpruce.com). Threadlube and Sealube are produced by Fleet Industries.

BeelzeBob
04-28-05, 02:48 PM
I think that there is a difference in Japanese philips head screws and US philips head screws...at least on the motorcycle philips heads that were installed 30-15 years ago.... I could NEVER find a philips head screw driver that would fit them correctly and it would always cam out and slip despite the valve grinding paste trick that I have tried many times. The only thing that ever seemed to work was to take a slightly oversized philips bit and drive it into the screw head and then use the impact driver on it. When it came out, throw it in the nearest garbage can and replace with an allen head fastener. There is such a side variety of philips head screws that many of them just do not fit a screw driver well at all unlike the uniformity seen in the other styles of fasteners. As an example, philips head bits fit and grip drywall screws extremely well but the same bit does not fit a Jap philips head and wants to cam out. It is like they make the philips indentation with sloped sides rather then square sides.

dkozloski
04-28-05, 03:36 PM
If you start researching "cross-point" bits it looks to me like the choices are endless. A good smack on the screw with a hammer first thing kind of extrudes the metal down into the recess; pick a bit and drive it into the screw with another good blow and you are ready for the first try. Where you are really limited in what you can do is when the structure surrounding the screw can be damaged easily such as aircraft skins.

steelhrd
04-28-05, 09:49 PM
The question is why so many headgasket failures in the northstar. Regardless to what certain indiviuals on the forums say my personal experence and local research is telling me the headgasket is the flaw of this engine. Now i am not a engineer or a mechanic but i am astute enough to recognize that there must be a problem when i know maybe 10 people who own this engine and 3 have or had a headgasket failure non of them with more than 110000 miles. all well serviced. mine failed right after i had coolant service performed.

dkozloski
04-29-05, 12:29 AM
steelhrd, I keep coming back to the same point myself. One of the problems with dealing with an institution like Cadillac is that the guy that is responsible for the head and gasket design has a vested interest in swearing up and down it is okay. If he admits it is now, and always has been a big screwup on his part he loses face. Engineers are just like doctors and scientists in that there is an unwritten agreement not to break a fellow professional's rice bowl. Since it isn't going to kill anybody the rest of us aren't going to know what the real situation is until the lawsuits begin and the lawyers start discovery. Until that point we are going to be hearing from a lot of people with failures and Cadillac saying:"The problem doesn't exist. The problem can't happen and I have a set of numbers to prive it. It's all your fault because you didn't maintain it. Even if it is a problem it isn't any worse than the standards set for the 1928 Oakland". What we are needing here is full disclosure instead of stonewalling. If there is no problem Cadillac can show us the data and shout it from the rooftops. If there is a problem that is more widespread than they are willing to admit they need to be dragged in front of a judge that owns a Cadillc with blown head gaskets.

Stoneage_Caddy
04-29-05, 01:26 AM
But ....He OWNS a northstar .....

well it sounded valid at the time but maybe he turns them over before warrnty runs out ....he probably makes more than the 5.15 per hour i do ....

but i have to also agree with Dkoz ....i wouldnt want to bite the hand that fed me either ....

i really belive its a maintenace issue myself ...but i cant bringmyself to buy a used northstar car ...ive had alot fo oppertunitys but the engine scares me from a longevity standpoint ...used ot be becuase it was so advanced but i see some of the issues here and i wonder about buying a used one ...

1996deVille
04-29-05, 12:55 PM
Stoneage,

Get a used one with 20K or so, drive it a couple of years and get rid of it before the problems start to show up. Two years will be about 30K, so dump it at 50K and start over again.

You'll spend far less $$$ overall by doing this and save a lot of time and energy. The biggest challenge with these cars is that once you're over 50K you'll spend repair/replace dollars so fast that the total price of the car will be nearly the price of one with 20K in a very short time. AND in the end, once past 50K the car becomes worthless for trade.

I foolishly went the route of a 4 year old car w/ 68K to start. When the head gasket goes on this car it is off to the junk yard. Next time I'll do it with better thinking!

Or, I'll rebuild a 60's Cad and have far less into it than a new car...

Much success

haymaker
04-30-05, 04:35 PM
The discussion of N* blown head gaskets, overheating and pulled head bolt female block threads has been ongoing by someone nearly everyday. Some of the people on the forum like myself have already borne the cost and personal labor of replacing the head gaskets and time-serting the block ourselves. We do have some insight as to what is involved in the repair and right or wrong a theory or two as to the cause of our N*ís head gasket failure. What I have noticed is that the N* owners that have never seen the inside of their engine and hope they never need to are forced to use their imaginations when they read posts on this topic. If the picture of the model I have fabricated is viewable it may be useful for some to understand the proximity of the head bolt, time-sert and head gasket in the N*?
The model was fabricated from wood and painted then all text was added using the computer. I used one of my old N* head bolts to help everyone gain a better understanding of the scale. Since the cylinder block is the location of the head bolt cavity, female head bolt threads and also the location of the time-sert when installed, I placed most of the detail in this area.
The cylinder head half of the model is only in place for reference has very little detail and is only to scale from the top of the head gasket to the bottom side of the head bolt washer. Any of the posted dimensions may very slightly biased on overall head bolt length (length may very by production run or manufacture but not by much). Bbob stated the thread engagement should be 2.5-3.0 diameters of the head bolt, which is an 11* 1.5 mm bolt. I measured at least 10 of my old head bolts for thread engagement and they all checked close to the same dimension so I will use the last one measured as 1.063Ē which = 27.01mm. 27.50 mm would be a perfect 2.5 diameters of thread engagement and I would call that close enough to the design target. The one interesting thing, (at least to me) was the length of threads on the bolt 1.853Ē, that measures out to 0.790Ē or a little more than ĺĒ of unused threads. When I look at the head bolt cavity it appears as though by just a small change in the tooling and machining operations (raise the upper drilled depth by ĺĒ then tap this ĺĒ along with the bottom 1.063Ē and one could easily increase the thread engagement to 1.853Ē or 4.34 head bolt diameters, with little or no added cost. I understand that there must be many other reasons that I am unaware of for not increasing the thread engagement but if there are any concerns of the blocks female thread failure, why not give them a little free help?
I detailed the water jacket to show its proximity to the head gasket, cylinder and head bolt cavity. The head gasket in the model is to size as to thickness but appears larger because of the shadows cast during the taking of the picture. Near the bottom of the head bolt cavity I shaded in red the area where a time-sert would be installed if required. BTW the time-sert doesnít increase the blockís thread depth engagement much maybe 1/16Ē if that, it only increases the square inches of surface area biased on itís larger outside diameter thus a lower psi loading in the immediate time-serted area of the block.

Please forgive my feeble attempt at show and tell using this model. You may find slight differences in the dimensions of your N* compared to my model. I would much rather have sectioned an old N* to use as a model but I donít have one lying around in the garage. Sorry about the orientation of the picture but to upload it at its largest size (800*600) I had to rotate the picture 90 degrees.

eldorado7
05-02-05, 10:02 AM
bbob...you seem to know alot about blown head gaskets...I now own a 96 eldorado w/N* engine...have been told it has a blown head gasket...spoke coming out the tail pipes, upper intake plenum leaking...rebuilding the head...a couple of weeks after I purchased the car it was leaking coolent...found out it had a cracked radiator...replaced it...it never ran hot on me...has 130,000 miles...in your opinion do you think it is a blown head gasket and if so what are the steps to rebuild the head...also where can I order timeserts...really need help....thanks

BeelzeBob
05-02-05, 01:49 PM
bbob...you seem to know alot about blown head gaskets...I now own a 96 eldorado w/N* engine...have been told it has a blown head gasket...spoke coming out the tail pipes, upper intake plenum leaking...rebuilding the head...a couple of weeks after I purchased the car it was leaking coolent...found out it had a cracked radiator...replaced it...it never ran hot on me...has 130,000 miles...in your opinion do you think it is a blown head gasket and if so what are the steps to rebuild the head...also where can I order timeserts...really need help....thanks


From what you said there is no way to tell what is the problem.....a leading/stuck injector can cause white smoke out the tailpipes, too.

The only way I know for sure to diagnose a leaking head gasket is to make an adapter from an old spark plug shell and use it to apply 120 PSI shop air to each cylinder with the piston at TDC and watch the cooling system for bubbling. This is a sure fire test to check the head gaskets.

Upper intake plenum leaking...???....the intake is one piece so not sure what you are talking about. An intake leak would have nothing to do with a blown head gasket. Be more specific or descriptive as to what you are talking about here.

www.timesert.com

There is rarely anything to do to the heads at 150K other than to scrape the old head gasket off, clean up the deck surface and bolt them back on. The valves, valveseats, stem seals, etc....will last virtually forever. I would not consider touching the head based on my experience and from what I have seen on this forum. BTW....it doesn't "warp" or anything either.

There is a huge amount of info in the archives on this subject. Use the search feature to search for "timeserts" "head gaskets" etc....and read up and save me some typing.

dkozloski
05-02-05, 01:49 PM
FWIW, if you watch the Nextel and Busch races regularly as I do you will observe that if water is ever added to any engine, at any point, for any reason, it is a gone gosling; they never survive to the end of the race. It makes no difference if they guessed wrong on the tape on the front or punch a hole in the radiator; if it boils, it is terminal. Sometimes if they catch the overheating soon enough and make corrections before you see steam it is okay; it appears to be a matter of luck. The point I am making is that I am not surprised that cars with an overheating history that includes losing coolant, deteriorate to blown head gaskets on a regular basis. Maybe there is something to be learned here. These race engines are assembled by the very best mechanics in the world that are aware of every trick in the book. Nothing gets by them for long. Yet head gaskets blow for them. Why should factory cars be any different?

gtm2u
05-03-05, 09:44 PM
BTW gtm2u.....I had a thought or two driving home about our discussion here.....
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So, pardon me for making fun of Lancia or Fiat or anyone else...but stating what either of those did 40 years ago is not really that impressive either.
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So, that is why I was questioning why you thought that they are necessary or even an advantage. I still wonder, explain it to me.

You implied that the clamp load of the Northtstar production head bolts was barely able to contain combustion pressures. I supplied you with data to the contrary. Never heard back.

You make a lot of noise about what I don't know and what my motives are.
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I get on here to help people that have problems with their cars and engines. That is my main goal. I occassionally run across someone like you that is just not convinced that we might know a thing or two. If you want to talk, talk. Otherwise, please, let's stop the name calling and BS.
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Hey, even dkozloski and I occasionally agree and HE puts up with me to some extent so I can't be that much of an idiot...am I...??? LOL LOL

I'll state it again, I joined this group to LEARN and discuss the problems of this engine. I have been met with nothing but insults and ridicule and you misuse your office to promote this at my expense. Yet you never use a search engine to even figure out if Lancia is still in business much less what they have done and are doing. You sadisticly delighted in screwing with me and misrepresenting just about every post I made to validate either yourself or some point to obscure _MY_ goal. I try to talk around you with other members and you are still there in my face needling.
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As I explained early on the reason for studs was strength, AND this included to reduce the stretch which my best guess is the yo-yo / accordion effect every time it goes through a heat cycle. Thus with zero stretch it would have to rupture the whole threaded length in a catastrophic failure rather than 1 thread at a time. With 2" thread length the chances of pulling that out would be nil.
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You were right about the bolt calcs for I had had made a math error, however, that does not negate that these are pulling threads and not breaking bolts. I found the thread pitch on a used bolt to be questionable, I also found that threading a New Timesert on the used bolt went about 1.5 diameters before if fouled.

I repeated what I was told by a dealer mechanic which was some sort of publication existed when he was working at the dealer. His statement was that some initial advisory was to use Heli-coils. Those are the only 2 things that have been included in my posts which were either wrong or cannot be proved.
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I did make a lot of noise because you have acted totally irresponsibly towards me, not with the intent of providing dialogue but as stated to misuse your office to screw with me. While I've cited my work history you have falsified or misrepresented what I have written time and again.
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I too log on to a internet list of 50,000+ members where I am considered to be senior staff and one of the most helpful. I can assure you this crap has never existed, and anyone that has acted as you would have been a ghost for it's so counterproductive. I did not throw down a personal gauntlet, that's not who I am, but you have long since crossed the line with me.

There are some good people here with a reasonable sense of perspicacity that don't need to act like a jerk. Yes I did make a lot of noise, you have shown that you are capable of misrepresenting or lack of knowledge on countless occasions. At least when I go home I know I fixed something or I dealt fairly and respectfully with people.

BeelzeBob
05-03-05, 10:14 PM
I'll state it again, I joined this group to LEARN and discuss the problems of this engine. I have been met with nothing but insults and ridicule and you misuse your office to promote this at my expense. Yet you never use a search engine to even figure out if Lancia is still in business much less what they have done and are doing. You sadisticly delighted in screwing with me and misrepresenting just about every post I made to validate either yourself or some point to obscure _MY_ goal. I try to talk around you with other members and you are still there in my face needling.
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As I explained early on the reason for studs was strength, AND this included to reduce the stretch which my best guess is the yo-yo / accordion effect every time it goes through a heat cycle. Thus with zero stretch it would have to rupture the whole threaded length in a catastrophic failure rather than 1 thread at a time. With 2" thread length the chances of pulling that out would be nil.
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You were right about the bolt calcs for I had had made a math error, however, that does not negate that these are pulling threads and not breaking bolts. I found the thread pitch on a used bolt to be questionable, I also found that threading a New Timesert on the used bolt went about 1.5 diameters before if fouled.

I repeated what I was told by a dealer mechanic which was some sort of publication existed when he was working at the dealer. His statement was that some initial advisory was to use Heli-coils. Those are the only 2 things that have been included in my posts which were either wrong or cannot be proved.
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I did make a lot of noise because you have acted totally irresponsibly towards me, not with the intent of providing dialogue but as stated to misuse your office to screw with me. While I've cited my work history you have falsified or misrepresented what I have written time and again.
.................

I too log on to a internet list of 50,000+ members where I am considered to be senior staff and one of the most helpful. I can assure you this crap has never existed, and anyone that has acted as you would have been a ghost for it's so counterproductive. I did not throw down a personal gauntlet, that's not who I am, but you have long since crossed the line with me.

There are some good people here with a reasonable sense of perspicacity that don't need to act like a jerk. Yes I did make a lot of noise, you have shown that you are capable of misrepresenting or lack of knowledge on countless occasions. At least when I go home I know I fixed something or I dealt fairly and respectfully with people.


Geeezzz....I honestly tried to open a dialogue with you. You show up once a month and hurl insults, might light of the mistaken info you posted while insulting me for questioning it, provide nothing new to the debate and leave in a huff....only to reappear in another month after I've forgotten what you said the last time.

The offer is still open. If you want to input something constructive....like tell us how well Lancia is doing....I am not into doing internet searches to prove YOUR point. The fact is that no-one has heard from Lancia on this side of the pond for decades.

Your comments above are somewhat difficult to understand. DO you propose studs to reduce the stretch (more strength..??) or to add stretch. IF you want to make the joint stiffer then that is not going to be fruitful as the joint will be so stiff that it will crush the head gasket in compression when thermocycling and it will rapidly loose it's resiliency and fail much faster.

The joint is set up with the correct spring rate bolts. There are millions of Northstar engines running successfully that demonstrate this.

I still wonder about YOUR engine. Is it leaking at the head gaskets or are you just trying to redesing the joint in anticipation of the day it might fail because of what you have read on the internet.

No one is showing you any disrespect...but no one is going to be bullied or insulted by you either. Stick with factual debate and we can carry on. If you really read thru the entire thread of this post you can obviously see that not everyone agrees with each other but the conversation continues. Get the chip off your shoulder and join in. I am using my "office"....LOL LOL I am just another poster like you. Post away and use your "office"...


BTW...if you think that I DON'T help people on this forum then you must only read this post. We cover a LOT of bases other than just head gaskets on Northstars and a lot of help gets given and problems solved and failures diagnosed and repairs. They take the good with the bad and so should you.

gtm2u
05-03-05, 11:32 PM
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The one interesting thing, (at least to me) was the length of threads on the bolt 1.853Ē, that measures out to 0.790Ē or a little more than ĺĒ of unused threads. When I look at the head bolt cavity it appears as though by just a small change in the tooling and machining operations (raise the upper drilled depth by ĺĒ then tap this ĺĒ along with the bottom 1.063Ē and one could easily increase the thread engagement to 1.853Ē or 4.34 head bolt diameters, with little or no added cost. I understand that there must be many other reasons that I am unaware of for not increasing the thread engagement but if there are any concerns of the blocks female thread failure, why not give them a little free help?


Thanks for the model and picts, my '94 has a head thickness of 3.0" from washer seat to head gasket. My bolt hole depth is 3.17" with a bolt length of 5.48".

I see no reason to not use as much of that 3.17" depth as physically practical. The Timesert is .500" O/D so why not to forget the insert and tap for a 1/2"x13 N/C stud 6.75" long? It's not violating the block anymore than the insert, it's in keeping with the later coarse thread which should have been employed in the beginning, however it does require drilling the head bolt out .038". What's your take on this?

gtm2u
05-04-05, 12:47 AM
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have been told it has a blown head gasket
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do you think it is a blown head gasket and if so what are the steps to rebuild the head...also where can I order timeserts...really need help....thanks

Actually there are several methods which are used to check for a blown head gasket.

With the engine properly warmed up one is a clear plastic cylr to which a blue solution is added, this is placed on the radiator fill opening and a squeege bulb is used to draw any air / exhaust gas through the solution which changes from the dark blue to yellow. Many of the chain auto parts stores will rent these, a bottle of fluid is about $6 and should last a life time for the occasional mechanic. In the case of the N* you may need to fabricate a plug for the overflow bottle since this is a non standard hole size.
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Another method is to use the tail pipe sniffer used at smog stations which is held in the overflow bottle for the N* or radiator opening on most other cars.
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The 3rd is a rather expensive portable combustion gas sniffer in the $300-$600 made by various tool suppliers such as Snap--on which is much faster response time but unless that's all you are doing few mechanics own them.
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I have used the solution type for 30 or 40 years and with only one exception never had a failure to properly diagnose a blown head gasket. The exception was from a Nissan (where I worked) which would only leak when cold from sitting overnight but within 2-3 minutes of warming would seal back up and show no leaks. This is contrary to standard automotive practice of always checking when hot.
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The Timeserts can be purchased from the dealer for under $3 each, don't know if you can buy direct from the maker but might save a few bucks. The job is cost prohibitive at dealer prices so you had better gear your head up for the job of your life. The book time is 22-23 hours if you know what you are doing and have all the tools and a lift. There seem to be enought posters here to help you through the rough spots but you must have a manual before undertaking this task.

If you have anti-freeze coming out the exhaust just put your hand in the smoke cloud and let some collect, then give it a lick test, if it's sweet it's anti-freeze.

If you have a stuck injector it will smell like raw gasoline.

Cheers,
GTM2u

steelhrd
05-04-05, 03:54 AM
O.k. i'm wondering about my bolt and my friends bolt and the guy at the dealerships bolt whose headgaskets failed. While this maybe acceptable to you a car which i know is well maintained because i have the service records headgasket shouldn't fail at these mileages at the price i paid for this car. My wife's honda accord has 170000 miles and the most extensive work we have had is an alternator and some supension work which is to be expected. Other cars at this price point generally do not have failures of this magnatude. If it were not for my personal encounters with owners of this engine who have had the same problem i might be inclined to say i got the lemon.Gtm2u please remain active as i am a fan of this car but i will not purchase another until this problem is solved