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57K views 65 replies 28 participants last post by  AlBundy 
#1 ·
When I owned my '95 ETC, the dealer told me to hit it hard once a week. I was reluctant, but did so once every two weeks. They told me it was very important for the Northstar engine. Not only does it clear out carbon - but it does something else..

Does anyone know what this 'something else' is? I trusted my dealer so I did it and had no problem doing it. But, I can understand why one may believe that the dealer just wants you to beat on your car to break it..

Any thoughts?
 
#27 ·
Katshot said:
Unfortunately,
Many (if not all) the tests that engineers run on test engines are NOT directly applicable to production engines run on the street.
The tests are usually run on engines that are hand-built, necessary because the production tooling isn't in place. In a subsequent conversation with my friend at GM, he said that production engines are actually more consistent than the hand-built ones. The production tooling and process can put a group of engines together much more consistently than a single person or group of people can.

Seeing the results of durability tests on hand-built pre-production models is impressive, and I think that track record only gets better in the real world. Yes, some engines have issues -- it's impossible to build a perfect engine that will never have defects, but it's getting closer as time goes on. I do think that the track record for the Northstar, being essentially a clean-slate design, is impressive. The reliability of, say, a 350 Chevy is pretty good because they've had 30 years to tweak and improve the design. The Northstars had a production run starting in about 1993 and continuing on to 2000, essentially unchanged. In 2000, they changed the combustion chambers and piston tops to effect a slightly lower compression ratio, enough to recommend straight 87-octane. For 2004, they're adding variable valve timing, on BOTH the intake and exhaust camshafts.

It's a world-class design that had to have the bugs worked out for sure. Caddys first high-compression V8 in 1949 probably wasn't stone reliable either. It takes time to see what the issues in the real world will be and how to improve them.

I don't know if I spoke to your comment or not...I just started rambling. :) What do you mean, "actual competition"?
 
#28 ·
There's an actual competition among factory (and non-factory) cars that just runs the cars flat-out on a banked track until they blow. I remember reading about it a couple years ago in a magazine. As I recall though, there weren't any Northstars there.
Oh, as far as the production engines vs. hand-built units. I agree that mass production of engines leads to greater consistancy BUT, that also means that if there's a flaw in the manufacturing process, you get a WHOLE LOT of engines with the same flaw. This is what has caused problems several times for Cadillac. I'll agree that IF the engines are built EXACTLY as designed, you'd have some great engines. The problem is making that happen. I remember a couple years ago, one specific issue was that the holes for the head bolts weren't drilled quite deep enough in the block. This in turn caused head bolt torque to be reached before proper head gasket clamping load was attained. Guess what that caused? How 'bout several THOUSAND Northstars with head gasket failures, broke-down Cadillacs on the roads, pissed-off customers, service bulletins, recalls, legal notices, etc. etc. etc.
So you can see how a TINY screw-up in manufacturing can keep a GREAT DESIGN from being a GREAT ENGINE.
 
#29 ·
Yeah, absolutely, the process has to be nailed down before production can start. I don't remember reading about that endurance run. If those other vehicles can run at redline for 300 hours, then I'd say that they've matched what the Northstar was designed and validated for.

I've also never heard of thousands of Northstars blowing head gaskets because of a manufacturing flaw. If there's an article somewhere, that'd be an interesting read. I know that mine's performed flawlessly for 112,000 miles. Only major thing has been an alternator. Recently, I think the water pump is starting to weep, so I need to change that, which I'm happy to do after working on my old Cutlass. Water pump change on that car was about a 4-6 hour job. On the Northstar, about 45-60 minutes, including draining the fluid.

After I get the water pump changed, I'm looking forward to the next 100,000 miles! :thumbsup: I think low mileage is overrated anymore. The car with the least mileage we own is the Cadillac (112k). My Nissan truck has 173k and both vehicles run like brand new. Manufacturing and production have sure come a long way since a few decades ago. I remember when people would throw the car away (or at least change engines) at 90-100k.
 
#31 ·
The saying "they don't make them like they used to" is so true. Decades ago, the manufacturing process was so loose, they'd have three different piston sizes for one engine, A B and C. After the block was bored, they'd measure the bores and assign a size to it, either A B or C. Then they'd match the piston to that bore to ensure a proper fit. That's making three different parts to fit one hole, simply because the boring process wasn't accurate enough. Wow! Today, they can put that investment into superior metallurgy, better production processes, and more sophisticated designs.
 
#32 ·
So what do you think the verdict is: Important to push the northstar or any engine, or are the risks of messing something up outweigh the benefits?
 
#33 ·
I look at it this way. It's certainly not going to hurt the engine by pushing it hard every now and then. I'd agree much quicker to a statement like "it's good to wind the car out to keep the engine clean" than to a statement like "it's good to always idle the car around and be as easy on it as you can".

There's certainly a middleground there that will be different for everyone. On gmforums.com, IceHeart400 has a nitrous kit on his Northstar-powered Eldorado and races it often. He'd agree in a heartbeat that revving it to the moon is good for it. There are some other folks who would rather drive it slowly to moderately and call that good, perhaps nervous to push it to its limit. I'm used to engines with redlines of 4500 or 5000. The Northstar made me nervous at first to push it all the way to 6000, but after conversing with this powertrain engineer at GM, I'm convinced of the capability and durability of this engine. It's been bulletproof so far for me.

I guess that's all I can say. After my own experiences and discussions, I know the engine was designed for that and it can handle that. I think the worst thing you can do for any given engine is never drive it hard. Running at redline all day is not necessarily good for any given engine either. Moderation is key, just like with everything in life. :)
 

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#35 ·
I can agree to a certain extent. I dont think that it is good for the engine, but on the other side it doesnt really hurt it.
 
#36 ·
I will shed my experiences on this topic. The Audi 5000 and Acura that I had before were always driven as hard as they would possible go. The Audi was my first car and it had gone through two transmission rebuilds. When I first got my license I drove it as fast as it would go everywhere I went. I thought I was invincible. It was a great car it would top out in third gear (3 speed auto) at a little over 120 on the 120mph speedo and that was about 400 rpm into the red on the tach (approx. 6000). That 5 cylinder 20 valve engine was fun and I never had any problems with that car burning any oil. The 1990 Acura Legend coupe I had was another story. My uncle got it in as a trade and I ended up with it. It was faster but the handling was definitely not GERMAN and it smoked a little when it sat idling. I sold it to a friend after I bottomed it out over a stupid man hole cover and cracked the tranny casing after having the transmission rebuilt. I put every piece of aftermarket performance equipment I could buy on that car. That car lead to me losing my license for doubling the speed limit because some cop decided to "play games" with me when I had the flu. I now have a 97 sls and that is due to the fact that my uncle is a Cadillac Sales Manager. He knows how I beat on four wheelers, my father's big block boat (MerCruiser 454 loves redline 4400-4600rpm), and all the Automobiles I drive. Which car does he think will hold up to my abuse? A Northstar which was defnitely not my first choice. BTW, he has also told me to make sure that I "clean it out" every once in a while. I assured him that this would not be a problem and he laughed.
 
#37 ·
Welcome aboard, Mike! Thanks for signing up.. Well, I bet your Father knows what he's talking about being a Cadillac Sales Manager.. I'm sure he hears a lot of stuff around the showroom and repair bay.. And if he tells his Son to "clean it out" every once in a while, he can't mean any harm.. I still have to wonder - just a little - if the service people are actually made to think this and believe it.. But, I have a feeling it's the right thing to do. It just makes too much sense to me..
 
#38 ·
I agree. The thing that concerns me is not the engine, but the tranny. If you do it constantly then it could really mess it up, or definitely shorten its life span.
 
#39 ·
Some more input:

Drive it, keep the carbon cleaned out with frequent applications of throttle as you describe. Heavy throttle and higher PRM all tend to keep the ring grooves cleaned out of carbon as the higher RPM operation tends to cause the rings to move and rotate in the grooves which keeps them mobile and free. Babying it too much will allow the rings to stay stationary and eventually stick from the carbon buildup.

That is from my GM engineer friend, this time, posted at the message board at caddyinfo.com. Thought this was interesting, given our recent discussion.
 
#40 ·
Well, cant go wrong with that. Next time I get to my fleetwood, and there isnt a fricken foot of snow on the road, ill open her up!

Either that or donuts......
 
#41 ·
See here is what I don't get. Everyone opens them up on the road right? What about opening it up sitting in the parking lot in park. That can't be bad on the transmission and other then putting a load on it is equivilent to running it on the road. Correct me if I'm wrong but won't a few redline throttle pumps in the parkinglot do the same?

-Roswell-
 
#42 ·
Roswell256 said:
See here is what I don't get. Everyone opens them up on the road right? What about opening it up sitting in the parking lot in park. That can't be bad on the transmission and other then putting a load on it is equivilent to running it on the road. Correct me if I'm wrong but won't a few redline throttle pumps in the parkinglot do the same?

-Roswell-
Revving the engine up in neutral does little or nothing helpful. The time at WOT is so brief that there is little or no chance to build any cylinder pressure and heat before the engine is bouncing off the rev limiter. Revving it at part throttle puts little or no gas pressure load on the engine and pistons - it puts a lot of inertial loads into the crank, bearings, rods, etcetera - but nothing that does any good to the engine. Forget it. Put the car in gear and go drive it.

There are many advantages to occasional full throttle accelerations with a Northstar and any engine. It keeps the carbon cleaned out of the combustion chamber. This is maybe a little more important with the Northstar than some other engines due to the tight squish volumes between the piston and the cylinder head. This is designed this way to promote good incylinder mixture motion (good combustion) but it has the down side of providing a ready place for carbon build up to touch the piston causing noise. Ever heard of the Northstar "cold carbon rap" problem? Simply put you'll hear a rythmic, piston slap like noise when the engine is cold. Very prominent and very annoying. Cause: excessive carbon build up causing the the piston to contact the carbon on the head causing it to rock in the bore and "slap" - much more evident when the engine is cold and the pistons haven't expanded to full diameter yet. Simplest and easiest "fix" for this: A few good WOT accelerations to clear the carbon out. That is all it takes to eliminate the problem and prevent it from re-occurring.

Occasional WOT accelerations also help seat the rings to the ring lands and exercise the rings and keep them mobile and from becoming stuck in carbon in the ring lands. At high RPM and WOT the rings move around on the piston. They actually rotate on the piston and will polish away any carbon and seat themselves to the sides of the ring grooves. This is especially important on the 2000 and later Northstars which had hard anodized top ring lands on the pistons. Very hard and wear resistant. Also harder to breakin and seat the rings to the sides of the ring lands to promote the best possible seal. Many oil consumption complaints on the 2000 and later engines are related to some extent with the rings never seating to the sides of the ring grooves due to lack of load as the engine was babied around forever. Even engines with rings stuck in the ring grooves due to carbon build up can eventually be freed up with enough high RPM operation.

WOTs warm up the engine thoroughly and clean out the exhaust due to temperature in the exhaust and high flow rates blasting particulates, rust and such out of the system.

Frequent WOT operation will not hurt the engine or the transmission. It's designed for that. The healthiest engines that I have seen at high miles are always the ones that are run the hardest. Rings are free on the pistons and sealing. No carbon buildup.

The exercise that I think works best for many things is to select manual 2nd gear on an isolated stretch of expressway. This takes the trans shifting out of the question if you are worried about hurting the transmission, also. Start at 55 MPH or so and go to WOT in 2nd gear and hold it until the RPM reaches near the normal shift point ie 6500rpm for an L37 and 6000rpm for an LD8. Hold the throttle wide open until the engine reaches, say, 6200rpm for your STS and then just let completely off the throttle. Leave the transmission in 2nd so that the engine brakes the car and creates some pretty heavy overrun conditions at high vacuum levels. Let it slow until it is about 55 or so and then go to WOT again and repeat. This exercise really loads the rings, allows variable RPM operation at WOT for several seconds continuously, creates heavy overrun which tends to unload the rings and make them move and thus exercise them in the ring grooves and it will blow out carbon and the exhaust - all without creating a spectical of yourself and attracting the attention of the cops. You can do it on most any freeway and stay within the 70-75 MPH range allowable. Once a week like this will keep the engine cleaned out and healthy and is DEFINITELY recommended for the Northstar in particular.

The Northstar engine was designed, developed and validated to be run hard. It was expected that people would use the performance of the engine, though few seem to do so. The biggest single problem that many issues stem from is lack of use at full throttle by the owners. It just doesn't like to be babied around. The rings are low tension by design for good high RPM operating characteristics and low friction/good power. They work best if "used" and kept free.

In every conversation with owners I've had, once the owner started doing the WOTs and using the power and the engine they report no more carbon rap, better oil economy, no "smoke" when they do light it up (keep the exhaust cleaned out. If you notice a "cloud" when you do a wot you are not doing enough WOTs) etcetera. A bit of judicious use of the other end of the throttle travel is a good thing.
 
#43 ·
Katshot said:
There's an actual competition among factory (and non-factory) cars that just runs the cars flat-out on a banked track until they blow. I remember reading about it a couple years ago in a magazine. As I recall though, there weren't any Northstars there.
.

Katshot. Where and when does this happen. I want to go. This is a figment of your imagination. Ridiculous. Who would fund such an endeavor, what would it prove and why would anyone do it? Nothing like this happens but if it did a Northstar would do very good at it.
 
#44 ·
Anthony Cipriano said:
Revving the engine up in neutral does little or nothing helpful. The time at WOT is so brief that there is little or no chance to build any cylinder pressure and heat before the engine is bouncing off the rev limiter. Revving it at part throttle puts little or no gas pressure load on the engine and pistons - it puts a lot of inertial loads into the crank, bearings, rods, etcetera - but nothing that does any good to the engine. Forget it. Put the car in gear and go drive it.

There are many advantages to occasional full throttle accelerations with a Northstar and any engine. It keeps the carbon cleaned out of the combustion chamber. This is maybe a little more important with the Northstar than some other engines due to the tight squish volumes between the piston and the cylinder head. This is designed this way to promote good incylinder mixture motion (good combustion) but it has the down side of providing a ready place for carbon build up to touch the piston causing noise. Ever heard of the Northstar "cold carbon rap" problem? Simply put you'll hear a rythmic, piston slap like noise when the engine is cold. Very prominent and very annoying. Cause: excessive carbon build up causing the the piston to contact the carbon on the head causing it to rock in the bore and "slap" - much more evident when the engine is cold and the pistons haven't expanded to full diameter yet. Simplest and easiest "fix" for this: A few good WOT accelerations to clear the carbon out. That is all it takes to eliminate the problem and prevent it from re-occurring.

Occasional WOT accelerations also help seat the rings to the ring lands and exercise the rings and keep them mobile and from becoming stuck in carbon in the ring lands. At high RPM and WOT the rings move around on the piston. They actually rotate on the piston and will polish away any carbon and seat themselves to the sides of the ring grooves. This is especially important on the 2000 and later Northstars which had hard anodized top ring lands on the pistons. Very hard and wear resistant. Also harder to breakin and seat the rings to the sides of the ring lands to promote the best possible seal. Many oil consumption complaints on the 2000 and later engines are related to some extent with the rings never seating to the sides of the ring grooves due to lack of load as the engine was babied around forever. Even engines with rings stuck in the ring grooves due to carbon build up can eventually be freed up with enough high RPM operation.

WOTs warm up the engine thoroughly and clean out the exhaust due to temperature in the exhaust and high flow rates blasting particulates, rust and such out of the system.

Frequent WOT operation will not hurt the engine or the transmission. It's designed for that. The healthiest engines that I have seen at high miles are always the ones that are run the hardest. Rings are free on the pistons and sealing. No carbon buildup.

The exercise that I think works best for many things is to select manual 2nd gear on an isolated stretch of expressway. This takes the trans shifting out of the question if you are worried about hurting the transmission, also. Start at 55 MPH or so and go to WOT in 2nd gear and hold it until the RPM reaches near the normal shift point ie 6500rpm for an L37 and 6000rpm for an LD8. Hold the throttle wide open until the engine reaches, say, 6200rpm for your STS and then just let completely off the throttle. Leave the transmission in 2nd so that the engine brakes the car and creates some pretty heavy overrun conditions at high vacuum levels. Let it slow until it is about 55 or so and then go to WOT again and repeat. This exercise really loads the rings, allows variable RPM operation at WOT for several seconds continuously, creates heavy overrun which tends to unload the rings and make them move and thus exercise them in the ring grooves and it will blow out carbon and the exhaust - all without creating a spectical of yourself and attracting the attention of the cops. You can do it on most any freeway and stay within the 70-75 MPH range allowable. Once a week like this will keep the engine cleaned out and healthy and is DEFINITELY recommended for the Northstar in particular.

The Northstar engine was designed, developed and validated to be run hard. It was expected that people would use the performance of the engine, though few seem to do so. The biggest single problem that many issues stem from is lack of use at full throttle by the owners. It just doesn't like to be babied around. The rings are low tension by design for good high RPM operating characteristics and low friction/good power. They work best if "used" and kept free.

In every conversation with owners I've had, once the owner started doing the WOTs and using the power and the engine they report no more carbon rap, better oil economy, no "smoke" when they do light it up (keep the exhaust cleaned out. If you notice a "cloud" when you do a wot you are not doing enough WOTs) etcetera. A bit of judicious use of the other end of the throttle travel is a good thing.
Anthony, my dad never drives his cars hard. How many miles would you guess before the carbon is built up to be a disadvantage to an engine like the N*? IE, every few thousand miles, etc.?
 
#45 ·
Anthony Cipriano said:
Katshot. Where and when does this happen. I want to go. This is a figment of your imagination. Ridiculous. Who would fund such an endeavor, what would it prove and why would anyone do it? Nothing like this happens but if it did a Northstar would do very good at it.
It would be interesting to see. Never heard of it from an auto manufacturer. But Mercury Marine does it, at least used to at their privately owned Lake X in FL. They ran outboards non stop, some models literally ran for years. There was one model, can't remember which one, they tied up to a dock and ran WOT for a reported 3 yrs, until it finally quit. They do it just to see what would break first. They would repair the failed part, start it back up and see what would break next. And on and on. And probably the reason they won so many Formula 1 Championships.

Here is a link to a Media Player Video. Check Part 3.
http://www.screamandfly.com/home/features/mercury_video_history/mercury_video_history.htm
 
#46 ·
For one, Marine engines dont run at WOT as said... an example, boss owns a new 30 ft Carver mariner 350, full throttle on it was both the engines at 4,000 rpms.

Our truck, Silverado 1500 w/Z71 (1998) is driven very lightly by mum and occasionally when I or someone else is in it, we have to floor it and man.. can you see the dust and griime flow out of that exhaust. Now its been needing a tune up and gets more of that carbon build up because the explosions arent as effectiant anymore. The catera, on the other hand; is driven quite hard but only because the engine like the Northstar was built to run hard. High-Rpms
 
#47 ·
JefferyG said:
For one, Marine engines dont run at WOT as said... an example, boss owns a new 30 ft Carver mariner 350, full throttle on it was both the engines at 4,000 rpms.

What do you think running at full throttle at 4000rpm? It's operating at Wide Open Throttle. Marine engines run at full throttle most all the time. That or they idle while the owner trolls. Anyone who has spent any time in a boat has held the throttle wide open for long periods of time. Especially any sort of sport boat. Marine engines are run the hardest of most any engines on the planet. Even to keep a large boat on plane the engines are deep into the throttle. Very deep. Put a vacuum gauge on a marine engine and you will see that they run at zero vacuum a lot. Zero vacuum is unthrottled and the only difference between that and true WOT is theoretical. Practically it is exactly the same thing. Boat engines are just usually rated for a specific power at a lower RPM than the equivalent engine in a car. With the propping and gearing in the boat the operating RPM can be kept lower to make the engines live longer even though they are at WOT a great deal of the time.

The Northstar engine was marinized for MasterCraft ski boats several years ago. It was exactly the same motor as was installed in cars. It was also propped and geared to run 6000rpm at full throttle in the boat - which it does frequently.
 
#48 ·
Lawrence said:
It would be interesting to see. Never heard of it from an auto manufacturer. But Mercury Marine does it, at least used to at their privately owned Lake X in FL. They ran outboards non stop, some models literally ran for years.

All automotive manufacturers do limit endurance testing of the cars and the engines. Just no one runs a bunch of different cars WOT on a track to see which blows up the first. All the engine durability testing takes place on an engine dyno. As an example, the Northstar engine is validated on a test on an engine dyno where the engine is run at full throttle, 6000rpm, making 300hp for 300 hours continously. The engine is shut down occasionally for checks and oil changes and such but when it's running it's full throttle at 6000 flat out. And it lasts 300 hours. In 300 hours at 6000rpm in a car that would be about 150 miles an hour and the car could go 50,000 miles. Twice around the world. It would be impossible, practically speaking, to accomplish this on a track so vehcile testing to the point that the engine would fail would be pointless. You would run out of tires and gas and such.

Dock testing by the marine manufacturers is very common. Everyone does that. GM Powertrain is a major supplier of marine engines and tests the same way but on a dyno. The main reason to "dock test" (tie it to the dock and leave it on wide open) is to test the cooling sytems in the boat and such. The engine testing on a dyno ensures that the engine will take it.
 
#50 ·
In my opinion, what's more sensible than occasionally rodding your caddy is to keep the oil and filters and plugs NEW, AND only place the shifter in fourth gear when you want to do extended cruising -- over 55. That prevents the car from loping along at low rpm (in fourth) in town, which contributes to carbonizing the intake, cyinders, and plugs !!!! I found quite a performance (and mileage) boost in new platinum plugs, (car only has 42k on it) but I just bought thew eldo from a little old lady. SO --- run you plugs for 100k if you want to, but I recommend you instead replace then about every 50k -- with the best plugs you can get (Like Bosch Quad Platinums) Style on, Ride On.
cs
 
#51 ·
elwesso said:
..........................Sure, some can endure more WOT than others, but there is no engine (that i know of) that is specifically designed to be at WOT all the time. End of story.
There are a lot of engines designed to run continously at WOT... Every engine is designed with a certain duty cycle in mind. Engines that power heavy trucks run wide open at peak power all the time. They are designed to do that and can do it for thousands of hours. Dedicated marine engines are designed for a "rated" power and can run that way for thousands of hours. Even simple engines like a 5hp Briggs and Stratton on a portable generator runs wide open all the time as long as the generator is loaded. It is designed to run that way.

A diesel engine in a commercial 18 wheeler can run at WOT maximum power for millions of miles. It was designed for that kind of constant power output. It runs at a relatively low RPM (below 1800rpm all the time) to keep the inertia loads low and makes the power/torque with compression, displacement and a lot of turbo boost and very very robust internal parts - allowed due to the low RPM it operates at.

A passenger car engine is at the other end of the spectrum. It will idle through life almost never running at full throttle. It will last hundreds of thousands of miles running at part load. It is designed to make a lot more power to accelerate and pull loads on an intermittant basis. Generally, an automotive engine will live at full load, full throttle for several hundred hours - not the thousands and thousands of hours that a marine or truck or aircraft engine might see under these conditions. It all depends on the duty cycle of the engine and what it was designed for.

You run your weed eater engine or leaf blower engine at WOT for extended periods - those were made for that. They are relatively low specific output engines for that very purpose - to live at a continous WOT duty cycle.

Many engines are rated at different power levels based on the duty cycle that they must endure. Gas truck engines are commonly rated at a number like 350hp in a light duty truck (an 8.1 GM gas engine in a suburban or pickup) or that same exact engine (same internal parts) would be rated at 280hp in a heavy duty truck that would tow 16000 pounds all the time. Or haul rocks out of the quarry in low gear and full throttle all the time. That same engine might be rated at 220 in a Kodiack truck that tows semi trailers short distances. But at full throttle all the time to keep them rolling. The engine is derated to be able to perform at it's rated power (WOT for that application) for thousands of hours that would be required instead of the hundreds of hours that it might see at WOT in the light duty pickup truck. The key to understanding is that there are many different duty cycles and each engine is designed, optimized and rated for that application. Many of the heavy duty engines spend all their lives at full throttle both gas and diesel varieties.
 
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