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DYNO Black Smoke out exhaust when let off gas after WOT

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Old 10-04-2005, 07:52 PM
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Default DYNO Black Smoke out exhaust when let off gas after WOT

CORRECTION IT IS a Hazy WHITE SMOKE

Nitrous is almost done. Ok I was dynoing my car to get a base line and the shop noticed something that disturbed me.

The car had a small puff of white smoke when they first started it up that went away right away. They also had the car apart and said my intake had oil puddled in it when they looked into the hole.

Then we dynoed it, and no smooke was coming out of the exhaust at all. Mycar was 12.2 A/F Ratio just FYI on that dyno run. Then we went WOT and went up to 6,500 or whatever the limit was and AS SOON AS THEY LET OFF THE GAS, on deceleration, a cloud of white hazy smoke came out oif the exhaust

On the nitrous run, they just did one. It only picked up 50 hp, but ran 13.0 A/F , so they didn't run it anymore. They put in Bigger Fuel Jets so I can get it lower and my goal is around 11.8 or so, but we haven't dynoed it again.

I have heads and Cam etc. seee sig. The smoke only happened on deceleration. What is this and is it safe? I was told it might be a Ring and the oil getting by.

Is my engine going to blow up???? Should I dyno it again with the nitrous?

Any information on this would be appreciated :thumbs:

Last edited by 2001 Red Coupe Bandit; 10-04-2005 at 08:05 PM.
Old 10-04-2005, 08:20 PM
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Could be ring problem, but if you got a puddle of oil in the intake looks like you need a catch can. Seems like the Crankcase hose is breathing in ALOT of oil in your case. Clean the oil up in the intake, then put on a catch can (you can make one from Home Depot for about $11) and then test the car again. If the smoking still continues, im afraid you may have ring problems.

But then again thinking about it hard for it to be a possible ring problem when it only happens when coming off the gas or sometimes during startup.

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Old 10-04-2005, 08:33 PM
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they may be fluttering a little on decel, they're obviously in good enough shape to hold pressure under accel.......if it was billowing smoke I'd look into it, but what you're describing , I wouldnt give a second thought...seriously
Old 10-04-2005, 08:35 PM
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It wasn't a puff of smoke, it filled up the shop pretty good, but again, only happened after the foot was off the gas, then the smoke came.

I think it was whitish in color, but it coul dhave been different potentially?
Old 10-04-2005, 08:41 PM
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may be pvc pickin up oil vapor loadin the cylinders,that's my best guess...... i've seen several cars do this on a dyno and not limited to LS based cars
Old 10-04-2005, 09:37 PM
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Oil in the intake tract could also be caused by rings. Compression leaking passed the rings blowing into the crankcase causing higher pressure than normal and forcing oil through the pcv. as far as smoke only on decelleration? i've seen lots of cars do this simply because decceleration enrichments were not set right. and a good tune can sometimes elliminate it completely. But not usually on to big of an injector.
Old 10-04-2005, 10:31 PM
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Wouldn't white smoke be indicative of coolant? I had the exact same scenario on my old motor blowing white smoke after a WOT blast on decel only.... turned out I was sucking coolant which was verified by a leakdown during a pressure test. After installing another set of heads the problem vanished.

Could be ring flutter/blow by as mentioned, but wouldn't the smoke be black?
Old 10-04-2005, 11:38 PM
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Sounds Like A Head Gasket Prob. White Smoke Is Usually Steam From Your Coolant. Pull You Plugs And See What They Look Like. If Thats What It Is There Will Be At Least One That Looks Different. Hope This Helps Ya
Old 10-05-2005, 03:05 AM
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Ive dynoed hundreds of cars that do the exact same thing. I dont think there is anything wrong with your car really.... The motors go into full vacuum when the throttle is closed and im guessing it sucks any oil in the intake pcv into the motor and burns it during decel.

Ive never seen a problem with most of the cars that smoke like crazy on decel...
Old 10-05-2005, 05:37 AM
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My car started to smoke when letting up on the gas on the dyno and at the track. In my case, a new set of valve seals cured the "problem."
Old 10-05-2005, 05:48 AM
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I have metal valve seals that replaced the plastic ones I originally had. These are Patriot Heads, but the guys at the shop didn't think the issue was the heads???

They thought it might be oil getting by the ring. Possibly needing a re ring or a new block to solve the issue. I don't want to do this, but you can get a new 350 Block for $2K (Plus labor) and that would be almost as cheap and easy as doing a re ring.

I just hope my engine isn't going to blow up. I wonder how you diagnosis it for sure, the smoke issue.

Again there was oil in the intake when they looked at it, so I know it is getting in there.

I have had the same PVC Unit on there for a while, maybe I need ot check it out again to make sure it is workign well.
Old 10-05-2005, 05:55 AM
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I've had some oil in the intake of both my 1999 Camaro SS and the 'Vette pretty much from Day 1. I don't think "normal" situation with these motors is going to cause the amount of smoke that you're describing.

Also, you say it's "white." Are you sure it's not coolant as some of the others have mentioned? Does the smoke smell like oil or does it have a coolant smell to it? Burning oil has a bluish haze to it and you should be able to smell it. It's pretty distinctive.
Old 10-05-2005, 06:11 AM
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I will find out today and look when they dyno it to see for sure. I hd some white smoke ocasionally out of the tail pipes when I 1st strated it up, but then it went away. It seemed to do it more when the engine was warm.

They seemed to think it was OIL. I mean there was oil in the intake and my car burns a little oil anyway, so I think it is oil.

It just has me very concerned and not enjoying my new nitrous that is on my car right now.

They will dyno it again today, but wanted to make me aware of the issue BEFORE they dynoed it again, especially WITh Nitorus., in case the car blows up
Old 10-05-2005, 07:38 AM
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Default have had the same experience

I had exactly the same thing happen with my '01 SS at a local shop while on the second dyno run of three during a tuning session. At the time the guys in the shop stated it was probably weak valve seals. The initial engine work was performed at MTI (who did not do the dyno runs) so I took it to them for diagnostics. The #7 cylinder will not hold compression during testing. The diagnosis is broken oil ring land on the piston, which in talking to them and a couple of GM mechs this is a fairly common problem with the LS1. Also it seems that once the engine develops this problem it will continue to be the weak link in the engine if you have the piston replaced. I'm told and have confirmed through several shops in the area that the only viable way to bring the engine back to the previous high level of performance with any reliability is to install a new short block. The $ being pretty much a wash whichever way you choose to go.
Old 10-05-2005, 01:12 PM
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I think you hit the nail right on the head. Neal Rings, and might as well get a new block



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