FASTFATBOY

Does your car do this? I have been told it's pretty common. Car makes great power, does not use oil on the street.

This car also puts a good bit of oil in the catch can, I have to empty it each session as it's half full. Uses a quart of oil a day on track, most is in the can.

Throttle body hoses are capped off for track use, I have dual catch cans vented to atmosphere. One from the left rear valve cover to a can and the other from the valley to a can.

The valve cover can is the one that fills up, the valley can is always dry.

I have tried numerous setups with the hoses, I have made it better with this setup now. It used to cover the back of the car in oil after a weekend with the hoses routed back to the throttle body.

Thoughts on the causes? Its driving me batshit crazy.

I have restricted pushrods for it but havent really run them yet.

Bad guide? Ring flutter? WTF?

Things I have done so far....

New valve seals

Pulled the valley pan and resealed the box.

Removed the PCV valve as it has the later model valley pan on it.

Compression is good.

Passed a leak down test.

Hi Volts Z06

Is this the original LS6? I had a huge problem with filling the catch cans on my last LS3 stroker (but no smoke). I was able to get it under control by properly plumbing the catch cans and PCV system. A vented breather with check valve was used on the passenger side while the driver's side was plumbed to the catch can. A second catch can was plumbed to the valley pan vent tube. Essentially you need to be able to use fresh air to ventilate the engine under vacuum and the check valve to close under acceleration to avoid oil blowing out the breather. I'll try to find a picture of the exact routing because I'm struggling to remember exactly.
All this goes away (ideally) if you go to a dry sump due to the scavenging effect.

FASTFATBOY

This is a GM crate LS6, not the original LS6....that's why I took off the pcv valve as it has the later style valley cover.

I put an extension in the oil filler cap with an AN to the oil can,on street tires it was ok...on slicks it filled up the can QUICK....made a huge mess.

The oil smoke is caused by either coming by the rings or a valve guide on decel I think. I was told these engines have ring flutter.

I have restricted pushrods I will put in it, this should help with the cans filling up. The car makes too much power and runs too good to have a major engine issue.

SunnydayDILYSI

It's not real common, but you're not the only one. I'd guess about 1/25. There is another C5 driver that I run with about 6 weekends a year that has had that problem for a couple years now. He's had a couple LS engine experts do a lot to the motor trying to fix it, but they haven't found the cause.

ZedO6

Data point: my 2002 C5Z with 21K burns zero oil on a track weekend with M1 15-40 run about a qt over. I did the valve springs and seals before I put it on the track. DRM oil cooler, no cats, batwing air filter, otherwise stock engine. I don't add much oil between oil changes either (3 track events usually), maybe 1/2 qt. Used almost exclusively on the track. I don't baby the car, but I'm not bouncing off the rev limiter either.

I'm a believer in running negative pressure in the crankcase like the car is setup from the factory. With the stock crankcase breather, I don't see much oil in the intake either. I read that wasn't the case when you were running that way. I'd put my money on valve guides the way it smokes on trailing throttle. If it was getting past the rings you'd see deposits on the plugs.

davidk72008

I noticed your car was doing this coming into turn 5 at Barber's the day I talked to you up there earlier this year. I just assumed it had something to do with the extra oil added for track days. Hope you figure out what is going on

FASTFATBOY

I talked to a guy at Schwanke race engines which is where I bought the restricted push rods.

They build a lot of LS based road race engines, he told me he sees this all the time, gets calls on this problem regularly and saying I am far from being the only one who tracks their C5 fighting this issue.

He told me it won't hurt a thing for the car to do this, as many do it. He also told me the only way to truly fix it is:

Pull the engine down, put in a better piston/ring package like Mahle.

Or put a dry sump on the car.

For reference I built a LS1 bottom end with Mahle pistons and rings that had a complete top end off a C5 Z06 including the cam. I tracked this car for 5 years with no issues. It did the same thing out of the exhaust but it was very very light.

I had one catch can on the line from the valve cover to the throttle body everything else PCV related was stock. Now I know this car did not generate NEAR the grip the Vette does, but braking was similar.

The smoking I might could deal with, but the oil control with the cans is a big concern.

FASTFATBOY

Yes, drives me nuts. Did you get you a car?

C5 Hardtop

The '99 Z28 SS (LS1 w/piston slap), the '99 C5 Hardtop (w/piston slap) and '04 Z I tracked hard would use 3/4 to a full quart of oil in a single track day. Track days were typically 4 20 minute sessions. That is a lot of oil to use. Never had a problem and didn't do any catch can mods. It does look bad. If that matters and/or your track has big sweepers (and you have track tires), go with the experts advice and do a non-gm dry sump install.

SunnydayDILYSI

The oil in the catch can is very common. Most folks that I know running stock LS1 and LS6 engines go through about a quart a day at the track. Me included.

MX621

if my catch can (modified moroso) is routed back to the intake manifold on the track it fills the catch can up in about 3 sessions.. car started smoking real bad and thought... O NO!!! but was just the catch can full.. if I run it to atmosphere is get very little oil in the can.. im assuming the high vacuum levels in braking zones pull a lot of oil /vapor from the motor. so I just run it open atmosphere on track.

FASTFATBOY

I thought about running a hose from the bottom of the catch can back to the pan. Supercharged and turbo guys have to do this, any reason why it wouldn't work?

c5racr1

That catch can oil has a lot of other nastyness in it, a bunch of acid and blow by hydrocarbons. But you could run a return through the dip stick tube.

ddahlgren

Why would you vent to a catch can from the rear of valve cover? Do you have an air oil separator inline with the vent line that needs a new home rather than LR VC? Is the oil pan a street pan or road race one to keep the oil off the crankshaft and getting beat to death?

FASTFATBOY

Its a stock C5 Z06. Schwanke race engines recommended these changes. They told me to weld a #10 into the rear of the drivers valve cover and run it to a vented catch can. I was also told by them to cap the passenger valve cover off.

Rear of the driver valve cover did slow the oil into the catch can down, these cars are bad about trapping oil in the passenger valve cover and then running forward under braking.

I tried the separator cans inline, this was a no go as the car smoked like a pulpwood truck, so I capped the intake and vented the cans to atmosphere.

FASTFATBOY

Got pics on mounting?

Bluefire

I add the extra quart of oil before heading to the track. I do get a minute bit of oily carbon on exhaust tips and on the back of the car. No smoke though. Track use does seem to fill my catch can quicker.

My $0.02.

Bluefire

SunnydayDILYSI

I don't understand the point of the catch can if you are going to route it back down into the oil pan... The stuff in my catch can looks terrible, which is why I keep it in line and drain it when I can. Just make sure to add a bit of oil before each session.

FASTFATBOY

I keep my cans clean. If the engine pushes it out, it was going to be in there anyway.

I put my cans back on today along with the restricted push rods and an oil change. Cans are inline from the drivers rear valve cover line and the valley line.

You can rev the car to 5,500 rpm in 2nd gear and let off the gas, let the rpm come back to 2500 in gear, push in the clutch and pop the gas pedal and it lets out a cloud behind the car.

Car hauls ***, baffling I tell ya. Makes me want to rip the heads off the darn thing.