grantar2

Team,
the car in question has a stock L98 motor, 1990 6sp which is autocrossed regularly.

Engine has been resealed. Performance / power is excellent. However since all the leaks have been sealed I have noticed I pump oil out the dipstick.

I have searched the numerous threads here and other sites, and feel I am not getting enough pull off the PCV under WOT. I have brand new AC Delco PCV valves and fresh hose, nothing blocked. Was thinking of cutting in a breather but I a couple of the threads implied that one side the PCV sucks and the other it doesn't, not sure why I it would work that way. Seems to me that both the line running to the throttle body area and the other to the manifold.

What I was considering doing is putting a breather element in line between the PCV valve and the intake, with a T that can be capped for street driving but opened for track and autocross events.

Thoughts, examples of other solutins?

Thanks

Jimbo 89

Are you saying you have 2 PCV valves? 1 on each side? That's not the way it is supposed to be. Passenger side is only a vent.

USAsOnlyWay

On my 86 PCV airflow goes:

through the airfilter/MAF (metered)
tee'd off line to pass side valvecover (stock this is on your throttle body IIRC, no PCV)
through the engine crankcase
out through the driver's side PCV valve
into the intake manifold (vacuum source)

90 could be different, or you just have 1 extra valve.

rodj

Common problem with WOT operation.You have little or no vac on PCV system.
Under normal running cond , air enters pass cover , goes through engine and exits to intake through
PCV valve on drv side cover
@WOT , the fumes travel back up the hose from pass side cover ( which is the inlet air for PCV when you have vac
at PCV valve) to the TB .
Port for that hose is in front of throttle blades so only passing air "suction" ; not true vac
as if pulled from behind the blades like the PCV valve does
At WOT when you have greatest case pressurization , engine is only being vent by tiny 3/8" line with no vac on it

Short of a dedicated pan Evac system , possibly open breathers on each cover to relieve crankcase pressure (temp seal PCV valve ) and clean the mess off the valve covers at end of race?

Kubs

How many miles on the car? I would do one of two things. When my '90 got to about 100k miles it started sucking oil through the TB during track days. My solution at the track was to cover the tube on the TB with duct tape and put the hose back on. It didn't suck oil anymore but I pressurized the crankcase enough to blow the grommets out of the valve covers and spew oil all over the engine. I later tried breathers like you mentioned but then the oil comes out the breather and drips and burns on the exhaust. My final solution was to remove the PCV system and plumb both valve covers to a vented catch can. The problem was the rings were worn and allowing too much blow by. Now that you have replaced all yhe gaskets and stopped the leaks the oil is trying to find another way out. It sounds to me like a rebuild is in your future. Anything you do now will just be a band aid fix.

grantar2

Yep currently have two PCV. May be part of the problem. Do you have a photo you can share?

Thanks

grantar2

Photo when you have time would be appreciated. Thanks

grantar2

I don't mind band aids at this point given the car is primarily street driven for fun, and autocrossed. She has a 135K but doesn't feel down on power and her times are still good. Won BSP in Cal Club 2011.

vetteoz

Sure it is a PCV valve in the pass side cover ; not just the plastic fitting for the hose from TB?
If it is actually a valve then you would have no entry point for the air

grantar2

Yep my bad I have a PCV in both spots.

vetteoz

So your were screwed
Valve in pass side cover not opening because no vac from TB and valve in drv side not working
because no air available from pass side.
At WOT; totally relying on the crankcase pressure to blow fumes pass spring loaded closed valves

USAsOnlyWay

Yep, I take it you don't need the pic now? It isn't stock looking at all anyway, hopefully you are good to go now.

grantar2

Problem solved. Plumbed the system the way it's supposed to be, ran it hard to redline during testing and then 4 laps of solo competition and she was purfect.

Spharticus

Glad that worked out for you. I had the same problem with my 90. On a side note, check out my other post reguarding throttle body plates. that can also cause problems for the PCV system.

http://www.smokinvette.com/corvettef...t=21390&page=2