: Does this stand to reason - Get your engineering degree ready



codewize
04-25-07, 07:53 AM
Ok so in the past we have discussed HP vs Torque many times. I have a very good technical understanding of them at this point. So knowing what I know and understanding the principles behind each I want to know if this makes any sense.

We describe torque as pressure and HP as work or power. We also know that excessive pressure in the combustion chamber can contribute to head gasket failure by lifting the heads.

Secondly we know that adding a Volant CAI or other to the 2000+ cars decreases low end torque and adding the Corsa exhaust furthers the effect.

With both of those in mind, does it stand to reason that adding a CAI and exhaust will lessen the chance of a blown HG? Now I know that we also contribute the HG failure to poor coolant maintenance, but above and beyond that, does this make any sense at all?

jadcock
04-25-07, 09:41 AM
HP = work. With more power, the engine is doing more work. More air through the air pump = larger explosions. I don't like looking at torque as "pressure" in this situation because the pressure of the explosion produces work (HP). I'd say that any power-adder you add, you're creating larger explosions (especially at higher RPM, where much of the work is done).

Torque is a force. Electric motors produce torque at 0 rpm. You produce torque at 0 rpm, if you will. You can push all you want against a brick wall (exerting a lot of force), but there is 0 rpm, so you're not doing at work. But you can measure torque. And you can derive work done (HP) by looking at the torque and the speed at which that torque is measured.

HP = Torque * RPM / 5252.

http://vettenet.org/torquehp.html

eldorado1
04-25-07, 10:14 AM
We also know that excessive pressure in the combustion chamber can contribute to head gasket failure by lifting the heads.

1) A northstar is not a 1200hp dragster.
2) Thermal expansion causes more force on the heads than cylinder pressures.
2a) Many, many, many times more force.
3) Thermal expansion causes northstar head gasket failures through thread pull-out.

Ranger
04-25-07, 10:22 AM
More air through the air pump = larger explosions.
:tisk: There are no "explosions". The flame front burns across the cylinder in an orderly fashion like ripples across a pond.

eldorado1
04-25-07, 10:27 AM
I don't like looking at torque as "pressure" in this situation because the pressure of the explosion produces work (HP). I'd say that any power-adder you add, you're creating larger explosions (especially at higher RPM, where much of the work is done).


The cylinder pressure directly affects the torque. That pressure is just like someone pushing down on a lever. This torque changes with crank angle, which is why engines need flywheels to even it out.

Horsepower would be more of a function of how many times you can push down on that lever every second.

You can have a little man pushing on that lever a billion times a second, and have the same horsepower of a big man pushing the lever 10 times a second. That's why you can get a Zenoah 20-something-cc engine with more horsepower than a typical lawnmower. A 2 stroke already means you get twice as many pushes.

AJxtcman
04-25-07, 01:11 PM
Secondly we know that adding a Volant CAI or other to the 2000+ cars decreases low end torque and adding the Corsa exhaust furthers the effect.

With both of those in mind, does it stand to reason that adding a CAI and exhaust will lessen the chance of a blown HG? Now I know that we also contribute the HG failure to poor coolant maintenance, but above and beyond that, does this make any sense at all?

WOW I have only seen a couple of head gaskets blown on 2000+ Northstars.
99 and prior is a Different story. I believe it has to do with the block in this vintage.

jadcock
04-26-07, 08:38 AM
:tisk: There are no "explosions". The flame front burns across the cylinder in an orderly fashion like ripples across a pond.

Yes, that's correct -- I was referring to it in the simplest terms. A larger "bang" equals more output.

jadcock
04-26-07, 08:39 AM
The cylinder pressure directly affects the torque. That pressure is just like someone pushing down on a lever. This torque changes with crank angle, which is why engines need flywheels to even it out.

Yeah, you're right, I'll yield to that.

codewize
04-26-07, 10:53 AM
So again I say that if we do something that yields less torque it stands to reason that there is less pressure. Thus creating less of a chance for a failed HG. Yes?


The cylinder pressure directly affects the torque. That pressure is just like someone pushing down on a lever.


Yeah, you're right, I'll yield to that.

samm
04-26-07, 11:14 AM
no, there is no increased pressure in the cylinders at higher rpms. maybe a slight difference but nothing that will be noticed. whoever said before about thermal expansion was correct, that is the reason heads will lift, especially on engines that are NA. if your talking FI applications, the same is true- the air/fuel mixture pressure inceases yeah, but that itself is not going to lift the heads. it's the repeated ignition of the increased pressure. point being, on our N* heads would lift in most cases because of excessive usage at high rpms and high temps.

eldorado1
04-26-07, 01:57 PM
So again I say that if we do something that yields less torque it stands to reason that there is less pressure. Thus creating less of a chance for a failed HG. Yes?

Yeah, if you build a northstar that only puts out 250 lb ft at 8500 rpm (400hp) there will be less in cylinder pressure than stock (300lb ft). Head gasket will still blow for either one.

Aluminum expands huge amounts vs temp, putting huge loads on the head bolts. If the aluminum block threads can't hold that load, it will let go. Then the rest of the bolts follow.

jadcock
04-26-07, 02:13 PM
So I gather that what Eldorado1 is saying is that it's much more of a function of heat cycling than it is actual pressure, within reason.

eldorado1
04-26-07, 02:43 PM
Very much so. A 5" block of aluminum expands 0.0115" when heated 100C. (if I did my math right) Try stretching a bolt by that much and you'll see the kind of forces you're dealing with here. ;)

Ranger
04-26-07, 03:10 PM
Why didn't they just leave 'em cast iron engine like God intended.

AlBundy
04-26-07, 04:03 PM
:yeah:

codewize
04-26-07, 04:52 PM
Weight and strength. Milling ability.

eldorado1
04-26-07, 05:01 PM
Why didn't they just leave 'em cast iron engine like God intended.

You're welcome to go back to driving your 20hp Model T. I won't stop you.

:alchi:

Ranger
04-26-07, 05:19 PM
If they were cast iron, we would not be having head gasket discussions. Aluminum serves one purpose. It reduces weight. I don't think the trade off is worth it.

AlBundy
04-26-07, 05:38 PM
I guess Ford felt the same way when they made the new Shelby Cobra.

eldorado1
04-26-07, 06:03 PM
If they were cast iron, we would not be having head gasket discussions. Aluminum serves one purpose. It reduces weight. I don't think the trade off is worth it.

The design is solid. It was just a poor execution. Poor quality aluminum used in the block and/or bad thread choice.

Look at the all aluminum Ford 4.6L... introduced in 1993. No problems at all.

The Northstar V8 weighs as much as most V6's. That's with huge heads for those 4 cams and their hardware. Better performance and gas mileage is the result. Considering the Northstar is basically a race engine, a Cadillac may not have been the best destination for it. Lets face it - most of you baby your engine and don't care about performance. You don't drag race or autocross where 100# would make a huge difference. That's understandable.... it is a 4000+lb cadillac.

Raze
04-26-07, 06:28 PM
Just my .02, the bigger question which has finally been asked is material choice, expansion rates due to heat and head attachment method. Using hardened steel bolts straight into a threaded aluminum block with piddly thread depth is plain silly but you gotta wonder if it wasn't a first year engineer who did the heat cycle analysis on those threads and borked something :).

The simple solution to this whole discussion is headstuds, period. Timeserts are the next best since they have bigger threads, that's about it.

eldorado1
04-26-07, 07:23 PM
Head studs don't gain you anything over plain bolts, besides the more uniform clamp load for a given torque. Thread engagement is the same, so the problem is the same. The timeserts spread the thread over a larger area, just by using a larger thread diameter. So they can handle more without pulling out.

I think the design was good on paper, it just didn't transfer to real life (like so many things). You can test a lot of things on a dyno, but you can't simulate years of thermal cycling. I'm sure they realized the problem about '95, and put something into action for the 2000 MY. IIRC they revised it again for 2004 or something.

truant
04-27-07, 08:29 AM
Yeah.. what is our lesson learned??? NEVER buy a new engine design.. always let some other sucker try it out for 10 years to work the bugs out of the design...
Take the venerable 318 for instance.. I think its still made today and is one of the best performing engines ever made!

I never liked the 307 much.. but it sure was better than my N* has been.. I got 20mpg in my 87' brougham.. i get 24 in my high-test N* 99 deville.. my 307 never had worse problems than PCV valves and vacume hoses (thank god for the TBI350 in my 90' brougham) .. my first N* kicked the HG out at a measely 70k!
ohh well.. live and learn!

blb
04-27-07, 02:11 PM
Wow......this is real progress! A while back, very few members here would even admit that there was an inherent design/manufacturing issue with the Northstar and associated headgasket failures. Most would pass off the headgasket issues as a poor maintenance issue rather than a combination manufacturing/design issue, mainly because most would believe whatever bbob told them. I'm glad to see that the discussions are becoming more realistic based on real world experiences rather than failed theoretical calculations.

codewize
04-27-07, 02:52 PM
Has the HG issue been resolved at all. I mean do the 2006+ have the same inherent problems, or have there been more adjustments made like the 2000-2005.

What about the new 4.4? Is that a completely different engine? And BTW, what is that 4.4 in?

AlBundy
04-27-07, 03:10 PM
Wow......this is real progress! A while back, very few members here would even admit that there was an inherent design/manufacturing issue with the Northstar and associated headgasket failures. Most would pass off the headgasket issues as a poor maintenance issue rather than a combination manufacturing/design issue, mainly because most would believe whatever bbob told them. I'm glad to see that the discussions are becoming more realistic based on real world experiences rather than failed theoretical calculations.

I noiced this as well. There were members that wouldn't admit it but it alway in the back of everyones mind. I wonder how many members here pre Bbob's departure have had HG problems? :confused: A side note its good to see this lounge is comming alive again.:thumbsup:

eldorado1
04-27-07, 04:02 PM
Has the HG issue been resolved at all. I mean do the 2006+ have the same inherent problems, or have there been more adjustments made like the 2000-2005.

What about the new 4.4? Is that a completely different engine? And BTW, what is that 4.4 in?

I would say "yes".

Like AJxtc mentioned, the MY 2000 revision seems to have mostly fixed the problem. I think the 2004 revision to m11-2.0 threads probably put the nail in that coffin. Time will tell. The 4.4 is the supercharged northstar for the Cadillac performance line (XLR-V, STS-V, $75-100k cars). It doesn't share much in common with 4.6L's.

codewize
04-27-07, 08:21 PM
Good solid info. Thank you.


I would say "yes".

Like AJxtc mentioned, the MY 2000 revision seems to have mostly fixed the problem. I think the 2004 revision to m11-2.0 threads probably put the nail in that coffin. Time will tell. The 4.4 is the supercharged northstar for the Cadillac performance line (XLR-V, STS-V, $75-100k cars). It doesn't share much in common with 4.6L's.

danbuc
04-29-07, 12:44 AM
Anyone ever seen an F250 6.0L over boost and pull the heads?......It's pretty cool.

But yeah, like everyone has said....cylinder pressures do not lead to N* head gasket failures. The only negative affect that cylinder pressure has on the engine (which is a trait of all aluminum head engines) is a very, very, very tiny drop in compression due in part to the flexibility inherent in aluminum. That's why some guys still run iron heads, since they don't deform as much.

Anyway....that's about it. Maybe if you were pushing 10+lbs of boost through it you might have to worry about lifting the heads, but that's obviously not the case.

jadcock
04-29-07, 06:09 AM
Anyone ever seen an F250 6.0L over boost and pull the heads?......It's pretty cool.

Dad had a 2000 F-550 with the 7.3L Powerstroke. With the Banks kit, it would boost up to around 29 or 29.5 pounds with EGTs in the 1700*F range at full load. That sucker was a moose. I understand the newer diesels aren't quite as robust as the older ones. Does Navistar still supply them with engines?

danbuc
04-29-07, 06:48 PM
Dad had a 2000 F-550 with the 7.3L Powerstroke. With the Banks kit, it would boost up to around 29 or 29.5 pounds with EGTs in the 1700*F range at full load. That sucker was a moose. I understand the newer diesels aren't quite as robust as the older ones. Does Navistar still supply them with engines?


I think they do, but I can't be sure...been a while since I've done anything with Ford diesels....or Ford in general.

I had a friend at school that had an '03 F250 with just the Banks, tuning kit in it...I thin kit was the unit that give you like 5 selectable levels of performance or
something. He kept it on the low side most of the time, but when he turned it all the way up...that thing MOVED!!!

z06bigbird
05-03-07, 10:51 AM
I thought I understood diff, but now???? I now have a problem explaining it. Best solution is for me to re-read.

MonzaRacer
05-05-07, 03:42 PM
OK in actuallity you guys are missing the actual part that fails,, the head gasket.
Headgasket technology has came a long way in 10/11 yrs.
Also if the N* was in cast iron it would weigh in at over 1100 lbs. Cadillac wanted an engine that had broad useability, hense the DOHC design.
Now as any good engine builder will tell you that power is made by air flow. The simply thing an engine does is move air BUT we added a single cylinder at a time producing force onto the crankshaft (IE torque).
Now if we look at a ANY engine the trick is to TUNE it to make power in a proper amount(hp/tq level required) at the designed RPM range.
Everyone forgets that the small block Chevy has been a low rpm torque engine all the way up to a high winding speed maker pushing 600 hp and turning over 10k rpms and all this from a design made in the early 50's with a valvetrain design actually patented by Caddilac and used first by Caddy and Olds.
So in an engine of inderterminat bore and stroke, to build low end I will use smaller diameter headers and exhaust and a little more muffler restriction. It slows down the net flow efficiency of say a higher flowing cylinderhead/cam selection.Now mess this realtion up and your engine will drive like crap.
OK so we free up the volumetric efficiency of the induction and free up the volumetric efficiency of the exhaust and you will raise the performance of the engine and it does raise the power PEAK just remember that its making more power, easier at all engine speeds, you have simply changed the engine breathability.
I had a budy who pulled a 262 V8 out of a Monza with soda strw sized exhaust and a grossly restricted intake 2bbl set up, to say that it was a dog in a 3000lb street rod was an understatement.
Now the 262 was a 2 yrs abortion of a small block with a 3.1 in stroke and a 3.621 bore, So the SBC head design was compressed into the second smallest bore ever used(the 267 had a 3.500 bore but a 3.48 stroke) so it was crippled at the get/go.
So he found a small set of OLD street rod headers and and an old aluminum intake for old 265/283s and installed them an the stupid car with 4.10 gears would SCREAM and light the tires and before with cobbled exhaust and stock manifolds it ran like a dog.
He even kept the engine in till he saved for a good engine 2 yrs later, a 4340 steel cranked 383 with AFR195 aluminum heads. So not thinking he drops in new engine and slaps on old intake and small tube headers (they were something like 1 3/8 or 1 7/16, very small) and its a DOG again, plenty of torque but would never run over 3800rpm.
I tell him to borrow my RPM Air Gap itake, 780 holley and get new headers,,,tada it runs great.
Now you have an engine that has been finnesed into a smooth running engine and HG reliabilty aside they are awesome performers.
OK that explained.
Your best torque production is produced with the highest peaks cylinder preasure the camshaft(s) can produced. The cams are also designed to meet sniffer tests, not make great lowend torque or higher up power, they are to make a BALANCE of both when coupled with the cold air and free flowing exhaust.
Now degree all the cams to make the highest cyl PSI when cranking will give the theoretical most push the engine can make in present form. Redesign the cams or retard them an you make a different power curve.
Now as for the timeserts they do not make the head bolts anybetter they are an invention to 1:repair damaged threads and 2: provide for both a slightly greater holding capability and not destroy BUT to actually save said block.
Helicoils and Timeserts an all similar products have been around for years and if i remeber corrctly the Helicoil was first designed for either marine or Aviation use then made cheaper for current uses.
Again I have to agree with most on the fact that the HG is failing because of aluminum thermal cycling but industry has fought it with metalurgy for decades to reap the benifits of aluminums good qualities like machineability, lightness and price to produce (and your cutters will live longer too).
Now flip forward 10 to 15 yrs and we see much better sealing headgaskets and of course technology has came forward in N* design.
WE see SBC cam through the same redesign, with roller design with one piece rear main, then LT with reverse cooling.
Then they redesign a 90 degree V8 into a very precise/powerful unit.
If you dont like torque numbers changing get different cams,headers,induction designed that lower torque peak.
In all actuality just trubo it and you gain lots of torque with proper tuning.
Oh an dont tell me turbos cant make torque cause thats what an engine makes, torque.
Horse power is simply rpm, torque and cid in an equation.
what you should look at is average torque ,how flat the curve is and if it has any dips.
For an engine that can turn 8000rpm plus in stock form (not long but it will do 8kplus with good valve springs) with doodads and extra stuff tacked on and make good power ( I have seen one with big stuff 3 FI make 400+HP and on E85 it gained another 80hp over that and I dont have torque specs but will ask about them)no wonder I want to try the Aurora 4.0 in a project soon.
As for head studs they do hold tension better and would be my pick for head fasteners.
I dont like Torque to yield faasteners or regualr head bolts.
Anyway if parts dont do waht you personally want then design your own and look for fixes.
I am wondering if anyone had any tests with copper shim head gaskets,,, hmmm something to try maybe, with a graphite or moly type coating.
HMM now where is my SCE card ,,,,,!
Lee Abel
AFTERMARKET PERFORMANCE
PS I have 3 people who have switched to Evans Cooling NPG/R for coolant and they love it as it has stabilized thier temps a lot.(not that they moved around a lot it just works better and has a boiling point of 375F with no preasure cap.