aaronc7

Hey guys, looking for some ideas/tips moving forward in the diagnosis of the car. Here are the facts:

New forged piston/rod LS1, nothing crazy. Car is a 2003 Z06, so it has the LS6 valley cover with normal/external PCV valve.

Drove car 500 miles on motul 10w40 break in oil. Did a proper break in but didn't beat on it, 4000 rpm and 50 throttle max, varying rpm. No issues during this time...car ran great, didnt burn any oil, nothing abnormal at all.

Changed oil and starting to get into some WOT action and tuning on the car in prep for track day coming up.

Out driving the car today, I see smoke coming out behind the car (actually under the hood). Dipstick popped out, sprayed some oil around, hot headers burning it caused the smoke.

It seemed to smoke at high rpms under load, but also I had it smoke (actively spraying oil out the tube presumably) just holding rpms high 4000+ lets say (but engine in vaccum).

Drive the car home, look around the engine bay... Notice the shop put the catch can/pcv lines backwards--doh (pcv valve installed backwards basically).

I figure this had to be it, clean up the engine bay, go back out to confirm. It does it again, drive back home.

Take apart all pcv system components, everything seems to be OK... but I notice the internal filter on the catch can may be adding some restriction (very scientific mouth blow test). PCV valve seems to work fine. Compare to old pics to confirm PCV valve orientation etc.

I haven't driven the car since taking the can filter out, but that's my next step. Temp removing the whole catch can setup and new PCV valve are probably a good idea for good measure.

For my own sanity tonight I did a compression test on all cylinders. All were 220-225psi. Last one was a little lower, but I figured that might be due to the engine cooling off significantly and battery juice getting low, so I tested a couple other random ones-- both within a few psi of cylinder 8. I pulled out the leakdown tester but I was getting annoyed trying to get the cylinders at TDC (last time I just removed the rocker arms, made things easy). But the couple cylinders I did get to test showed like 3% leakdown at 100psi.

Any thoughts on this/ideas what to try next? Seriously stressing out over here... one thing after another. Obviously I have lots of blowby or it's not getting out like it should and thus going out the dipstick. Going to post my pcv routing below.

Karlw

iTrader: (5)

Excessive blow by due to ring gap being too big?

jimmyp3353

iTrader: (3)

At WOT you don't draw any vacuum so the PCV system isn't doing anything. You are getting pressure in the crankcase which I'm betting is due to blow by. This happens a lot when you break a ring land. The poster above me is quite possibly correct with the piston rings.

RockinWs6

That's not true, the system is designed so at WOT BOTH the intake and outlet for the PCV have full vacuum applied to them.............................................. .

aaronc7

in theory both the intake mani and throttle ports should have some 'suction' created by the fast flowing air in the intake/throttle (especially throttle where the diameter is smaller).

I agree it sounds like too much blowby issue, but the compression test/leakdown data is showing otherwise I think.

Next step is a little more troubleshooting with the engine on at idle and examine the various PCV hoses and things and see if anything stick outs. Will try it with the catch can removed from the equation as well. Might be able to recreate the problem with the car stopped by revving it some too.

If this comes back with no results, then I will do a full leakdown test and see if that comes up with anything... I didn't dive into full leakdown yet because compression results were so consistent across the board

i'll look further into the ring gap thing. it may simply be that this engine just has more blowby by nature and the stock config is not sufficient for whatever reason.

mOtOrHeAd MiKe

iTrader: (8)

You need to sort out the PCV system. There are fresh air and dirty air aspects to it, as well as manifold and pre/post-throttlebody inlets and outlets, and check valves. This all varies by application. Alternatively put a vacuum pump on it as you may be exceeding the stock PCV system's ability to function properly.

aaronc7

Yes... mine mimics stock PCV right now with exception to the catch can. The catch can and or pcv valve seem like the next logical thing to check/replace/take out of the loop.

MIGHTYMOUSE

iTrader: (59)

crank pressure release port on stock system is the forward passenger to throttle body. make sure the port through the tb is not clogged.

the pcv return port (having a pcv valve in the way) makes for a pretty useless crank pressure vent

if both are fine then you should consider moving up/away from a pcv system designed around 300hp and stock piston/ring clearances

JD_AMG

Try an oil breather cap with a one way (out) check valve?

aaronc7

Thanks mighty mouse. I was bothering you the last few days on facebook.

JD- I actually have one of those arriving on Monday. Have a track day next weekend and hope its good enough to get me by for that.

Long term I'm looking at getting a setup from mightymouse. Would have probably went this route originally if I had seen it in time. Right now priority is getting car in a state where it doesnt puke out oil before the weekend, lol.