Hi Performance PCV valve
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,225
Likes: 654
From: Thunder Bay
Hi Performance PCV valve
I've been fighting with my '79 for about two weeks now. Its had an intermittent rough running problem. I finally tracked it down to the PCV valve. Its letting in enough air to cause the car to run lean. I bought a new one today, but I wasn't able to get the high performance valve, so I bought the one for the base engine. After I installed it - same problem. I assume I have too much cam for the stock PCV valve and don't have enough vacuum at idle to close the valve. I did a search on this forum and found a couple of threads listing PCV valves for high perf engines, but they are all a straight design. The '79 uses a 90 degree valve. The straight ones really don't fit well. Will the PCV valve for an L-82 work any better with an engine that has 13-14" of vacuum at idle, or can anyone suggest a PCV valve that will work for me?
Le Mans Master
Joined: Oct 2010
Posts: 6,928
Likes: 841
From: melbourne florida
2023 C3 of the Year Finalist - Modified
years ago on cars with a lot of crankcase pressure we would use a check valve for a power brake booster.it worked fairly well most of the time .if that helped we would go to a vacu-pan system.the check valve may do it for you.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
FYI, pcv valves don't close at idle. They regulate themselves to roughly flow the their same rated amount at any vacuum.
Try one for a smaller engine, 6 or 4 cyl.
They do close completely for backfire (pressure).
Try one for a smaller engine, 6 or 4 cyl.
They do close completely for backfire (pressure).
Melting Slicks
Joined: Oct 2006
Posts: 2,417
Likes: 336
From: Texas
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,225
Likes: 654
From: Thunder Bay
Still can't figure out why this problem started all of a sudden. The PCV I installed is the same stock design I have used for 20 years. The carb has been on the car since 2002 with no problems. Suddenly the PCV doesn't work properly. I don't get it.
Tearing out what little hair I have left.
Racer
Joined: Oct 2003
Posts: 424
Likes: 9
From: Killeen Texas
Thanks. That's a great thread and I did read it. However the PCV valve listed in the thread is a straight design and doesn't fit well on a '79 engine. I'm hoping to find one with the 90 degree fitting like the original.
Still can't figure out why this problem started all of a sudden. The PCV I installed is the same stock design I have used for 20 years. The carb has been on the car since 2002 with no problems. Suddenly the PCV doesn't work properly. I don't get it.
Tearing out what little hair I have left.
Still can't figure out why this problem started all of a sudden. The PCV I installed is the same stock design I have used for 20 years. The carb has been on the car since 2002 with no problems. Suddenly the PCV doesn't work properly. I don't get it.
Tearing out what little hair I have left.
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
If you didn't need the 2nd port, I suppose you could always cap it.
Any chance your PCV grommet is old and needs to be replaced to ensure a tight seal with the PCV?
DC
Last edited by DC3; Jul 19, 2013 at 02:36 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I don't want a pro PVC and No PVC debate
But I would like to express the other side of the coin. No reason to have PVC. The variable vacuum leak plays havoc on any attempt to get correct A/F ratios on any carb.
Piston rings have the most blow by at Wide Open Throttle when the PVC is closed because of loss of vacuum. While cruising at max vacuum you get the max PVC flow and have to run richer jetting to compensate. What are the valve cover breathers doing?
No real performance motor runs PVC
But I would like to express the other side of the coin. No reason to have PVC. The variable vacuum leak plays havoc on any attempt to get correct A/F ratios on any carb.
Piston rings have the most blow by at Wide Open Throttle when the PVC is closed because of loss of vacuum. While cruising at max vacuum you get the max PVC flow and have to run richer jetting to compensate. What are the valve cover breathers doing?
No real performance motor runs PVC
Last edited by gkull; Jul 19, 2013 at 06:49 PM.
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,225
Likes: 654
From: Thunder Bay
Sounds like a lot of headache from a PCV valve. You are sure this is what the problem is. Should you go back and go thru the process of elimination again? I'm not questioning your mechanical ability, I'm just trying to say that maybe you should re-think the situation, as the PCV seems to be giving you a problem that you never had before f/ an unknown reason. Good Luck w/ this problem. Sincerely, Jimmy.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
If u don't want to use the intake vacuum u still have other choices. One is using the original type breather only which u can see are standard on GMPP circle track crate engines. Or u can purchase a dedicated vac pump to evacuate the crankcase and install in-place at your smog/AIR pump location (your '79 of course).
And i used to read on line instructions for converting a FORD smog pump into a vac pump for crankcase ventilation - the drag racers would use theese because they have high blowby with only 2 piston rings.
Now the exhaust type evacuation plumbing really only works at open throttle with hi exh flow and not a good option for the street driven car.
Good luck and please post what u find works,
cardo0
And i used to read on line instructions for converting a FORD smog pump into a vac pump for crankcase ventilation - the drag racers would use theese because they have high blowby with only 2 piston rings.
Now the exhaust type evacuation plumbing really only works at open throttle with hi exh flow and not a good option for the street driven car.
Good luck and please post what u find works,
cardo0
Le Mans Master
Joined: Oct 2010
Posts: 6,928
Likes: 841
From: melbourne florida
2023 C3 of the Year Finalist - Modified
I don't want a pro PVC and No PVC debate
But I would like to express the other side of the coin. No reason to have PVC. The variable vacuum leak plays havoc on any attempt to get correct A/F ratios on any carb.
Piston rings have the most blow by at Wide Open Throttle when the PVC is closed because of loss of vacuum. While cruising at max vacuum you get the max PVC flow and have to run richer jetting to compensate. What are the valve cover breathers doing?
No real performance motor runs PVC
But I would like to express the other side of the coin. No reason to have PVC. The variable vacuum leak plays havoc on any attempt to get correct A/F ratios on any carb.
Piston rings have the most blow by at Wide Open Throttle when the PVC is closed because of loss of vacuum. While cruising at max vacuum you get the max PVC flow and have to run richer jetting to compensate. What are the valve cover breathers doing?
No real performance motor runs PVC
