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Discussion Starter #1
Hey there fellas,
I was wondering... Is WOT the ONLY way to remove the carbon buildup in a Northstar. I have a 99 STS, if that makes any difference. Is there another way?..ie chemicals, cleaners,etc...

thanks

-Mike
 

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detroit99sts said:
Hey there fellas,
I was wondering... Is WOT the ONLY way to remove the carbon buildup in a Northstar. I have a 99 STS, if that makes any difference. Is there another way?..ie chemicals, cleaners,etc...

thanks

-Mike
Are you adverse to the WOT process? It's probably the most economical way to do it and it is good for the engine now and then. A good hard acceleration once in a while is good for most any engine.
 

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Discussion Starter #4
Kev said:
Are you adverse to the WOT process? It's probably the most economical way to do it and it is good for the engine now and then. A good hard acceleration once in a while is good for most any engine.
Im not really adverse to it. I just am scared that so much pressure and the engine revving high may lead to something else going wrong. I stil do WOT's, but I am scared to do it ALL THE TIME. Maybe I am scared because I have had to replace an engine already. Thank God I had a warranty or else it would have cost me $7800. I am just trying to avoid any engine damage, if possible. Anything else available in addition to Lucas?

-Mike
 

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detroit99sts said:
Im not really adverse to it. I just am scared that so much pressure and the engine revving high may lead to something else going wrong. I stil do WOT's, but I am scared to do it ALL THE TIME. Maybe I am scared because I have had to replace an engine already. Thank God I had a warranty or else it would have cost me $7800. I am just trying to avoid any engine damage, if possible. Anything else available in addition to Lucas?

-Mike
I would use Top Engine Cleaner (GM TEC) before anything from Lucas. Chevron Techron is also supposed to work well, at least for deposits, but you have to mix it 50/50 with gas before using it. I don't know how well Techron works for carbon, but TEC was made for carbon I believe. There is a procedure you can follow that involves putting the TEC in cylinders, leaving it a while, then vacuuming it out. Maybe someone can chime in here with the details of that. It's intended to free sticky and/or carboned rings. Or you could just remove the heads and clean everything up with a toothbrush. :)
 

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Top Engine Cleaner IS the best way. It's certainly not as fun as the WOT procedure but it is safer for the engine and does a much more thorough job.
As I recall, there's directions on the can but I used to use it as follows:
1. Warm engine
2. with engine at idle, induce the Top Engine Cleaner into the intake tract. This is easy with a carburetor, but still do-able with EFI. You just need to be a little more "creative". Basically, the theory is to get the solvent into the combustions chamber area and quickly stall the engine so you don't simply burn-off the solvent. You want it to remain in there to soak into the carbon. I leave it that way for about 10-15min and then come back and start the engine. I let it run for a minute or so, revving it slightly until the smoke clears fairly well. Then I take it out on the road and open her up for a couple WOT runs.
Things to watch out for:
1. DO NOT pour solvent into the engine after the engine stalls
2. Understand that when the engine is started, it will smoke BIG TIME, so make sure to park the car where tons of smoke won't cause a problem.
3. If you simply run the solvent through the engine and don't stall it and allow solvent to soak into the carbon, you aren't accomplishing much.
 

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As mentioned, GM top engine cleaner is the alternative method. More expense, more work and less fun. The Northstar was designed to be run long and hard. I forget the number but during testing they were run for hundreds of hours on end at WOT on a dyno at the factory. You won't hurt it. Take her out and whoop her! Here is a quote from our old friend and guru.

"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. It's designed this way to promote good in-cylinder 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 (wide open throttle) 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 break-in 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 particles, rust and such out of the system.

Frequent WOT operation will not hurt the engine or the transmission. They're 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 transmission shifting out of the question if you are worried about hurting it. 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 - i.e. 6500 for an L37 and 6000 for an LD8. Hold the throttle wide open until the engine reaches, say, 6200 for an 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 over-run 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 over-run 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 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/validated to be run hard. It was expected that people would use the performance of the engine - which few people seem to do. 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 have had, once the owner started doing the WOTs and using the power of 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" at WOT then you are not doing enough WOTs...) etc... A bit of judicious use of the other end of the throttle travel is a GOOD thing."
 

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Discussion Starter #8
So Ranger,
do you think the Top Engine Cleaner will provide approximately the same results as your 2nd gear WOT method? Which method will produce better results? Thanks,

-Mike
 

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Ranger, THANK YOU for finally clarifing the WOT technique with the quote from your friend.

Rangers Friend said:
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 transmission shifting out of the question if you are worried about hurting it. 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 - i.e. 6500 for an L37 and 6000 for an LD8. Hold the throttle wide open until the engine reaches, say, 6200 for an 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 over-run 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 over-run 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 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.
THAT paragraph explains exactly what should be done, and how to do it. I think that is the section that should be high lighted in the Tech Documents on this site. Now my only problem is the nearest expressway to me, I-75 is an hour away.
 

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While I agree that some accassional WOT runs aren't a bad thing, there needs to be some common sense applied to that paragraph though. I doubt anyone at Cadillac would stand by a statement that suggests "frequent" WOT runs are not in anyway bad for the drivetrain, or that the harder it's driven the better. Most, if not ALL OEMs have a rather dim view of customers thrashing their cars regularly. Somehow I have a sneaking suspicion that if you took your STS to the dealer with a drivetrain failuer and told them it happened at the track while racing, they'd probably think twice about covering the damage under warranty. I don't have an owner's manual but I assume there's something in it about racing the cars or abusive driving habits being cause for denial of warranty coverage.
 

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What about Top Engine Cleaner and other strong solvents vs. headgaskets, seals, insulators, etc inside the engine?

Especially with the "leave overnight part" that is sometimes recommended.
 

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detroit99sts said:
So Ranger,
do you think the Top Engine Cleaner will provide approximately the same results as your 2nd gear WOT method? Which method will produce better results? Thanks,

-Mike
I really don't know for sure but the WOT treatment is certainly easier, cheaper and more fun. Try a few applications. If it doesn't work, then you can always have the top engine treatment done.
 

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The Top End Cleaner method sounds too much like work. WOT is quick, easy, and harmless. In addition it costs waaaaay less and takes waaaaay less time than TEC.
 

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I've found over all the years I've driven and the many engines that I have built that the best carbon build up prevention is to take the long route to a familiar place and cruise it for 5 miles or more at highway speed in the one lower gear. This increases the RPMs slightly, doesn't overstress any of the drivetrain, increases the amount of fuel and temperature within the combustion chamber and helps to clear and or keep clear the carbon build up.
I've never had a problem, even with engines 11:1 or more that I've built. Of course, these engines were built to be rev'ed high, yet I would do the above procedure anyway just to be sure.
lry99eldo
 

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So do you shift into 2nd while you're going 55mph, or start in 2nd from a stop? I just want to be sure I do this correctly.
 

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:yeah: Why start at 55? That's better than half way to your goal. Start off as slow as possible.
 

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Get a spray bottle and fill it with plain tap water. Get the engine started and up to about 2000RPM. With the air filter out spray the water into the intake and watch the carbon come out the exhaust. Knowledgeable mechanics have been using this procedure for at least 100 years.
 

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So do you shift into 2nd while you're going 55mph, or start in 2nd from a stop? I just want to be sure I do this correctly.
Accept the fact that the engine and transmission controls will NOT let you break anything .................read the service manual on transmission controls protocol.

If your car is in otherwise good mechanical condition .......... Find a clear, deserted stretch of highway/open road. Pull to the shoulder and place the stick in 2 (This action says "This is my preferred gear"). Traffic all clear ??? Ease onto the road and, from a slow rolling start, stick the gas pedal through the firewall and leave it there.The car will accelerate in 1st and at redline it will shift to 2nd and continue to accelerate. Just before the 2nd gear redline - ~6300 rpm - flip your foot off the gas pedal and allow the engine to brake the car down to < 20 mph. The transmission will downshift as necessary to keep the engine rpm in the proper band. Miss the 2nd gear redline and upshift ?....... Coastdown and do it again. Lots of smoke and crap out the tailpipe first time ?? Do it again......... You'll get to about 80 mph or so at the foot-off-the-gas point.

Why did we put the stick in 2 ???? Because that forces the downshift at high rpm coastdown: The theory behind the "WOT" is to load and heat the pistons and rings to the max during forced acceleration - then radically unload them with high vacuum during the coastdown. This load-heat-unload-cooldown chips away carbon flakes and allows the piston rings to work in their grooves, further shedding carbon buildup.

Where does some carbon buildup come from ??? Granny, grandpa and city driving. Gears - the 4T80E will always protect itself and the engine - neither allowing an over-rev or excessively high rpm downshift. You can, if you have the track room, take the car to speed limiter cutoff with the stick in 1st - upshifts will occur ONLY at full load redlines. I know for an absolute fact that my STS will do at least 143 with the stick in 1 - that's also just above where the 3 - 4 redline shift occurs. Yes, these cars (VIN 9) will do over 130 in 3rd.

......... and that procedure explained by dkozloski is an old, time-honored method of cleaning piston tops......... DO NOT spray any solid water - mist only, and know that the procedure is not as effective in a throttlebody-long runner-center log intake manifold system as it is in a down-the-throat carburetor system. Large reciprocating aircraft engines have used water injection for high power application demands for a very, very long time.......... it slows down the combustion process and keeps max combustion pressure in the cylinder for more rotation duration - as well as cleaning the piston tops.

Of course, we could always read back through the entire thread - and post #9 - to get further insight ........... and, in answer to the original thread title, there's a sticky just above this thread which talks about the GM ring cleaning procedure using potent chemicals.
 
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