fatbillybob

Gents,

I race a C5Z with a stock LS6 for my class. Here is the problem. I had a perfect LS6 2004 motor with the orifice valve PCV. That motor never used any oil and I did NOT race with catch cans. The motor was getting tired with compression about 130 all across with excellent leakdown numbers. I have the motor rebuilt to stock specs for my race class.


So my problem is the new rebuild:
New motor pukes out 3oz of oil per lap out the passenger side valve cover into a catch bottle or into the motor. I drip so much oil I can't race because I cover the people behind me. The valley PCV leaks out zero oil. When at idle there is pressure that builds up on the passenger valvecover exit. There is a mild amount of pressure build-up at the valley PCV. When I plug the valvecover exit with my thumb I get a rush of air when I release it. There is no perceived change in volume of this air at the valve cover at idle vs. high RPM. The baffling in the passenger valve cover is OEM stock and intact.

At the exhaust pipes exhaust is clear. There is zero oil blowing out the exhaust.

Compression on all eight cylinders is about 150psi to max 155psi
adding some oil raises the compression no more than 5psi

leakdown is no more than 5% at 100psi on the reference gauge on any cylinder.

On the chassis dyno the motor makes exactly the power and torque it is supposed to make with my race class intake restrictor. This motor was broken in on the engine dyno. I have less than 50miles on this motor. How can 150psi compression make the right horsepower? Can compression go away in less then 50 miles of running?


How can I stop the oil flow out the passenger valve cover? Why is this happening?

All ideas welcome.

Thanks!

Pounder

rings seated ? end gaps too big ?

fatbillybob

Seated? Yes. Break-in was done on the engine dyno. Gaps should be fine according to the builder notes.

kp1

Well, you didn't have an issue previous to the rebuild but now you do. You have positive pressure building up in the crank case. I reckon that can only be produced by cylinder compression/fuel detonation that is finding its way to the into the engine internals.

Did you install a high volume oil pump? To be puking that much oil out the valve cover, you must have a whole lot of oil there to be pushed out the baffle. HIgh volume pump plus extended time at higher RPMs = not good for a road race car.

Bill Curlee

I AGREE! What oil pump do you have? If you have a LOT of oil in the top part of the engine at high RPM, its going to fill a catch can.

During the cylinder LEAK DOWN TEST? See if you are losing ring seal into the crank test. If you have ring blow by, You can hear it if you open the oil fill cap when doing the leak down test.

Are all of your oil drain back holes free and clear inside the head?

If you are building crank case pressure at idle, the PCV system isn't working properly or is being overwhelmed by how much leak by that you are having. See if you can switch to a NON ORFACE PCV and see if you have less back pressure.

Maybe the PCV orifice is clogged. Do you have good vacuum at the vacuum port to the crankcase?

See if one or more of your lifters is flowing more oil onto the head than should be.

Just brain storming to give you stuff to check..

BC

Bill

David@MMS

post pics of the connections before and after, not sure why you have the pcv system modified but that could be the first error.

engines built for racing usually have more blowby than stock. the stock pcv system is built to handle stock horsepower, which i bet you no longer have.

people understand that when the engine makes more hp they need to change the exhaust, or need to change the intake, etc. etc. but are baffled why the stock crankcase ventilation system cannot keep up.

(but first make sure you have it hooked up right) is it the same valley plate? what else changed when the engine was r/r?

fatbillybob

Bill...Thanks for the ideas.

David...Motor is stock rebuilt for my class so no added HP. I did not modify the pcv only played with it to figure out how it works.

k24556

I had a similar problem. Had to go to a GM#12577927 valley cover, the one for the 2004 year.

My current plumbing is:
GM LS6 PVC plug, driver side rear valve cover plug. (pic below)
cap on the rear elbow nipple, passenger side valve cover (pic below)
Front elbow nipple routed to top of TB (pic below)
Hose to catch can from the intake.
Return hose from catch can to valley cover nipple.

I get about 2 inches of oil in the catch can in 3 hpde sesssions. This engine has probably 80 or so track days and 50 k miles.

If your oil is staying in the valve covers, it is either a plugged orifice in the valley cover (replace!!!) or the oil is slow getting back (big pushrods and small holes?)

pm me with your email and I will send you some plumbing drawings that might help more.