[Z06] PCV system and valve placement.
Thread Starter
Pro
Joined: Aug 2003
Posts: 508
Likes: 4
From: Baton Rouge LA
PCV system and valve placement.
Why did GM design the PCV system placing the PCV valve in a horizontal position. I have yet to find a PCV valve that will seal properly in a horizontal position. I replaced my leaking PCV valve w/ a brand new one in the exact location and it still leaked. I then positioned the PCV valve in a vertical position and presto no more leaking. Has anyone else considered this over the years? Any input would be appreciated. I also purchased a Greddy catch can, but have not mounted the unit as of yet. We'll see if this resolves my minimal oil issue.
Le Mans Master
Joined: Mar 2002
Posts: 5,955
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From: PNW
Ideally, a PCV valve is supposed to be spring loaded. It is supposed to flow more crankcase vapors when the manifold pressure is high (ie, during wide open throttle), and flow virtually nothing at idle.
If the stock valve is not closing at idle, I doubt it would make much difference since there isn't nearly the blow-by produced at idle or low RPMs as compared to WOT at high RPMs.
The GM valve doesn't seem to be spring loaded (it rattles around, and probably why it's mounted horizontally), and I'm thinking it closes at idle (due to high vacuum) and opens up with larger throttle opening (low manifold vacuum), and will also act as a check valve if the engine backfires or the manifold pressure gets higher than the crankcase pressure.
I know a lot of guys get a significant amount of oil in their catch cans ... seems the stock PCV systems on the LS1 and LS6 don't separate the oil vapors very well, and frankly I don't think a different PVC valve will change that much. If the stock valve was stuck (didn’t rattle) then that could causes some issues.
Let us know what you see with the new valve.
If the stock valve is not closing at idle, I doubt it would make much difference since there isn't nearly the blow-by produced at idle or low RPMs as compared to WOT at high RPMs.
The GM valve doesn't seem to be spring loaded (it rattles around, and probably why it's mounted horizontally), and I'm thinking it closes at idle (due to high vacuum) and opens up with larger throttle opening (low manifold vacuum), and will also act as a check valve if the engine backfires or the manifold pressure gets higher than the crankcase pressure.
I know a lot of guys get a significant amount of oil in their catch cans ... seems the stock PCV systems on the LS1 and LS6 don't separate the oil vapors very well, and frankly I don't think a different PVC valve will change that much. If the stock valve was stuck (didn’t rattle) then that could causes some issues.
Let us know what you see with the new valve.
Last edited by ZeeOSix; Sep 14, 2006 at 03:29 AM.
Drifting
Joined: Jun 2005
Posts: 1,824
Likes: 1
From: Middleboro Massachusetts
Originally Posted by O2Thief
Why did GM design the PCV system placing the PCV valve in a horizontal position. I have yet to find a PCV valve that will seal properly in a horizontal position. I replaced my leaking PCV valve w/ a brand new one in the exact location and it still leaked. I then positioned the PCV valve in a vertical position and presto no more leaking. Has anyone else considered this over the years? Any input would be appreciated. I also purchased a Greddy catch can, but have not mounted the unit as of yet. We'll see if this resolves my minimal oil issue.
My oil in the intake issue has gone away into the history books once and for all with the catch can 
I need a new dyno tune anyway, but I can only imagine without the oil mixing with the fuel, the results of the tune will be alot more accurate using all fuel. I heard the oil will lower your octane. With mine this is critical with higher compression of the milled heads.
Last edited by zo6vetteman2003; Sep 14, 2006 at 06:45 AM.
Drifting
Joined: Jun 2005
Posts: 1,824
Likes: 1
From: Middleboro Massachusetts
Originally Posted by skeet
Where is the PVC valve?
