Maybe someone can point me in right direction. I've searched threads but cant seem to find a similar problem so not sure where to start.
Car is 02 Z
Has Lt'S no cats Ti's re-tune
Vararam CAI
Thats it.
Rest is stock.
Car is primarily my HPDE car. I'm trying to get into racing and moved up from an AWD platform.
Anyway, car runs fine, was set up for the track with HP fluids but for first time with car nothing crazy. Just wanted to get feel for the different set ups etc.
So halfway through 2nd session of day as i'm getting more comfortable I get black flagged.
Apparently the car was blowing smoke and they thought it was leaking.
Its not a leak. everything is dry.
I've since been doing some street testing to see if I could duplicate. I thought it was something simple like Pwr Steering overflow but thats not the case.
Here's what happens as best I can relay. If I stay on the throttle as I would at track above 4500 rpms for a while then let off then get back on a cloud of smoke comes out the back each time I re-accellerate.
Doesnt happen during daily driving on streets, has to be pushed hard initally to get it start. Then like clockwork, on-off-on-smoke. If I stay on the gas it doesnt smoke, its only after i let off, then get back on gas.
It doesnt seem to be down oil but I put extra in for track as suggested so its hard to tell and i'm sure its buring it up but I've not gone much mileage like this so no noticable loss yet.
Someone suggested it might be a small leak thats dripping onto exhuast somewhere but if that were case i would think it would burn as soon as exhaust got hot enough and not stop burning with the on-off scenario.
Any suggestions where to look first? Its totally stock motor, no FI, no cams no nothing. Just exhaust and tune. Car runs fine at idle, no hickups, just smoke. I cant get back to track till I fix this as I'll be taken off every time, i'm sure.
I didnt post this to track sections as I think its a regular car related issue not something related specifically to track but maybe.
I cant imagine all Z's burn oil when put into a cycle like this. I've seen many of them on the streets being pushed a little harder than Legal limits would allow. Never see them blow smoke so I I figure i have a problem not related to track duty.

 

Oh, yeah, the car has 40,000 miles. All service is up to date, all recalls attended to as far as the records show.

 

so are you saying the smoke comes from the exhaust? - or from under the car?. If exhausts, could be oil blown at high rpm through the pcv into the intake then burnt when you get back on it. Rare to see it that bad unless there is considerable blow-by. Was the oil level normal before/after the run?

 

My best guess would be valve stem seals although unlikely at only 40K miles. Engine is sucking oil past the seals on the high vacuum condition in the cylinders when you back off after high RPM. Second thing to check is the PVC system. If valve is clogged or inoperable it could cause this situation.

 

Since the cats would burn off much of any oil in street cars under these conditions you may not see any smoke from them.How many miles on this engine?If it were valve stem seals you would see smoke on a cold start up as that is when the oil actually leaks into the cylinder and then burns off at start up.

 

Car has 40,000 miles. Does not have cats. LT's to Ti's thats it.
Smoke only happens on high rpm pulls then off gas then back on gas again as if by running high R's somethings building up then releasing then being burned on the gas again.
Someone had suggested PCV issue but being unfamiliar with these cars I'm not sure how that would occurr only in a given condition. Wouldnt it always be "stuck/plugged" and therefore show the signs at all rpms.
There is no smoke that I know of at start up.
I can do a catch can, but I just dont see how a stock car would need one but agian, not familiar with these cars. My previous turbo'ed cars had catch cans and rerouted pcv systems cause of the excess pressure and higher miles and weaker rings etc. But I didnt see how a stock car with no additional stresses would have pcv issues but maybe its just a bad check valve?

 

Could your plugs be fouled--maybe you need to run a hotter
plug? !

 

Read this thread: http://forums.corvetteforum.com/auto...nsumption.html

 

Thanks for the link.
I was under the impression that with ring issues I should be seeing smoke at startup no? I may be wrong and I'm still researching the issue with the rings on the LS6 but Is there a way that rings would be bad only at certain rpms? I thought bad rings were bad rings. Agian, new to this car but I'm still as lost as I was day one. From research I'm learning the ring issue was supposed to be on '01's but mine is a '02 but the build date from the door panel is August '01 so is that an '01 car that would be part of the '01 issues? Or was the issue with the actual '01 motor which would be different than the actual '02 right?
I had 1 catch can installed prior to the past weekend and after first session while in paddock someone came up and says "hey just letting you know you're smoking pretty bad. The link from autocross seems to describe my issue exactly. So where do I start with diagnosis? I have taken car to a corvette specialist who suggested the catch can but obviously thats not the ticket. To diagnose rings other than compression check is there anything else short of full breakdown of the motor?
I figure the cost involved in RR just to do rings would not be worth it and I'll just do a crate engine. The pisser is that there doesnt seem to be a specific diagnosis and that bothers me. Once I get a specific answer I can make a decision but to dump the motor simply cause of the what might be is a bummer.
I'm gonna do more searching but if anyone has a link to the repair involving the re-silicone of the area in question that would be helpful.
I'm gonna search Valley gasket and see what happens.

 

Catch cans are nothing more than a placebo in my opinion, they serves as nothing more than a secondary oil vapor baffles and collection points, it does not solve the high crank case pressure issue.
I would start by reading the GM TSB, it's very informative. On some LS6 engines, excess oil consumption was caused by the PCV oil baffle to valley cover seal. I don't have an LS6 so I'm not familiar with the exact configuration of this piece.
The next step I would take is to perform a cylinder compression test or cylinder leak-down test to determine the health of the rings and valve seats. If this test shows the engine is healthy, then I would move to some sort of resolution.
The following modifications worked for me: I lowered my oil operating temperature while under high loads by installing an after-market radiator with an EOC, I rarley see >250 deg oil temps now; I switched to an oil with a lower volatility while at operating temp and a relatively high HT/HS viscosity rating for a 30W; finaly I no longer add the extra quart the owner's manual tells you to add when tracking the car. I run mostly auto-cross so this may not be as important for me, most of the road racers say it's important to have the extra quart for high speed high G load turns.

 

I am thinking that it has to do with the PCV. The way you are describing is it smokes after you get off then back on makes me think the vacuum is sucking in oil to the intake and then at WOT it comes out the tail pipes. A catch can would help this but I have one on mine and it definitely doesn't catch everything.

I hope it is something simple for you!

 

Appreciate all the comments I'm gonna review everything thus far again. I figured PCV due to the fact that I only get smoke after letting off the gas and then back on. I figured it was pulling oil due to vacuum somehow but I'm just not all that familiar with the ls motor to know where. I'm gonna start research cause I really dont think its rings. The valley seal I keep hearing about sounds possible. I've got to start taking things apart I suppose I just figured I'd get some starting points.
Gonna do leakdown/comp this week. If thats good go from there. If bad. Time for new motor I guess. They're not that expensive.

 

40,000 and now starting HPDEs ? you need a valve job, new valve seats and new springs.

Most likely you have oil blow by at the higher rpms on the track and that is why you where BLACK flagged.

The corner workers are good at their jobs.



I have 30,000 miles on my LS6 of which 20,000 are HPDEs. Each winter the heads come off, cleaned, Valve seats are checked, NEW Valves and springs EACH WINTER.

so that is about every 5000 miles.

Now all the engine sees is 3,000 to 6700. Very seldom does it get driven on the street.

LS6s can take one heck of a beating, but still need to be maintaned. Mostly springs and valves

use the Ti and Sodium filled valves. SS valves are so so for sustained high rpm use.

I also run a 3qt accu-sump and oil cooler. Best mods ever down to my engine.

 

and a new LS6 crate is not that expensive.

 

catch can? how is the cold air return routed on your car?

reversion is an issue at hi rpms with the PCV system.

 

Assuming the engine performs normally, I would try a catch can with some breather mods.

 

A catch can wont cure but only prolong the problem. and with the smoke the engine is not performing as it should

Pull the heads off and take a look

 

If the cause is ring flutter, taking the heads off isn't going to help either.

The 2 MOST likely causes:

1. PCV system allowing oil to get sucked into intake. Correctable with a proper catch can setup.

2. Ring flutter, which is usually high RPM, LOW load.

 

We see this problem quite often in HPDEs so no speculation is needed.

 

Yeah, I supoosed gonna start with taking heads off next week. Car had a catch can installed before most recent envent and it didnt change the smoke condition. But from reading I see there's 1 can set ups 2 can set ups etc. So I gotta start from beginning.
I bought the car with 40k on it. From what I know it had not been tracked prior to my purchase so its only got a few events on it. I didnt realize the heads were bad on the cars and needed refresh every season but I'm learing the car as I go. I'm gonna re-check the routing of the can thats in place now but after last event it didnt seem to have caught anything which is why I wasnt sure if I should continue focused on PCV. If it had something in it then I'd be leaning towards PCV.
I spoke with a few other c5 Z's last event that didnt seem to have the problem and they were stock motors as well with very little extra work done other than standard track duty things like extra oil and better fluids. Most were runnin 5-30 also.
Hope I can figure this out. Crate engine is inexensive enough but from experience I know that its never as simple as clicking the order button for new motor and expecting a week later to have a perfectly running car. There's always something comes up with that kind of work but if thats whats to happen thats the plan.