C-4 Wrong PCV ???
Thread Starter
Instructor
Joined: Jun 2013
Posts: 138
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From: Apollo Beach Florida & Michigan
C-4 Wrong PCV ???
I've read many of the C-4 PCV threads but haven't got an answer for this question. I'm a new owner of an 86. The previous owner just told me that he had replaced the PCV years ago, but the new PCV that he installed did not look like the old one. The new one had a plastic tee shaped top instead of the "L" shaped top of the old one. He said he just capped the extra connection and used the valve. I suspect he used a PCV from an 81-84 Corvette. Instead of the proper one for the 1986 L-98 engine. There are a few numbers on the valve, either 99 or 66 on the base. But I can not find a reference to them. The engine also has leaky valve cover gaskets, a low idle and stalling when cold. I will be replacing the PCV with the correct one, but doubt that it will have any positive effect on the the idle or the stalling. Does a wrong PCV's matter that much? Thanks Guys!
Instructor
Joined: May 2012
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From: co
not sure about that but i can tell you, the one you have, sounds like the one that my 84 uses
on the 84, the tee part runs a vacuum line to the evaporative canister.
wouldn't think caping that line out, would effect the operation of the pcv valve its self
on the 84, the tee part runs a vacuum line to the evaporative canister.
wouldn't think caping that line out, would effect the operation of the pcv valve its self
Pro
Joined: Mar 2013
Posts: 628
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From: Indiana
I don't know about a wrong one but a bad one can cause many different problems. According to my FSM it can cause oil leaks because pressure can build up in the block. Mine was bad and I had a small leak that I never found the source of but when I replaced the PCV it went away. It also caused my dipstick to keep popping out. Having the right one would be a good thing. They only cost a couple of dollars and while you are at it check the hoses and rubber mounts and change those also. The ninety degree connection on mine was pinched shut and also cracked and leaking. The pinched shut side effect was the oil leak and dipstick popping out and the crack/leak cause my engine to run lean and throw lean codes (SES). For less than $7.00 I replaced both and it made a world of difference.
Safety Car
Joined: Jan 2004
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Or '86 was a change over year
85 - 86 PCV
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
The '86 has an aluminum vacuum line that has a T in it. One side goes to the PCV valve and the other goes to the vapor canister. It's the "white" part of vetteoz's diagram. If you look closely, you can see the metal vacuum line in this pic (early '86 with cast iron heads -- the T is right in front of the front runner):
The correct PCV valve is part number 6487779, AC Delco CV774C.
.
The correct PCV valve is part number 6487779, AC Delco CV774C.
.
Last edited by Cliff Harris; Jul 24, 2013 at 05:09 AM. Reason: Corrected "vacuum canister" to "vapor canister".
Thread Starter
Instructor
Joined: Jun 2013
Posts: 138
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From: Apollo Beach Florida & Michigan
Thanks to you all, To sum up. Cliff, The engine picture you posted, and vetteoz the YDJ hose diagram (which is the one under my hood) you posted are both correct, although the picture and diagram are functionally the same, the hose lay out is slightly different. As was stated there is a tee in the aluminum tube ...... To further clarify, my owners manual does shows the CV774C PCV with the "L" shaped single hose connector as the correct replacement part for the 86 Corvette. And, yes my 86 does have the cast iron heads. My conclusion, from your input, is that the wrong PCV was installed by the P O and capped but unless there is some difference in the calibration ie. spring tension, there will be no functional difference. Thanks for helping a "stuck in the 60's guy" understand this new to me, 30 year old technology
Safety Car
Joined: Jan 2004
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Makes sense now because I could never work out why my '87 (alum heads ) had that same alum tube shown but with the end welded shut .
GM obviously just reworked the existing PCV tube and that setup was after the "T" on the valve itself and before they went with the
molded rubber hose on the later engines
GM obviously just reworked the existing PCV tube and that setup was after the "T" on the valve itself and before they went with the
molded rubber hose on the later engines
Thread Starter
Instructor
Joined: Jun 2013
Posts: 138
Likes: 4
From: Apollo Beach Florida & Michigan
Makes sense now because I could never work out why my '87 (alum heads ) had that same alum tube shown but with the end welded shut .
GM obviously just reworked the existing PCV tube and that setup was after the "T" on the valve itself and before they went with the
molded rubber hose on the later engines
GM obviously just reworked the existing PCV tube and that setup was after the "T" on the valve itself and before they went with the
molded rubber hose on the later engines
I changed my PCV to the correct one (CV774C) with the "L" shaped fitting. It did not solve the problem. Tomorrow I will try to see if there are any problem codes in the ECM. Wish me luck!
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Pro
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From: weems va
I don't know about a wrong one but a bad one can cause many different problems. According to my FSM it can cause oil leaks because pressure can build up in the block. Mine was bad and I had a small leak that I never found the source of but when I replaced the PCV it went away. It also caused my dipstick to keep popping out. Having the right one would be a good thing. They only cost a couple of dollars and while you are at it check the hoses and rubber mounts and change those also. The ninety degree connection on mine was pinched shut and also cracked and leaking. The pinched shut side effect was the oil leak and dipstick popping out and the crack/leak cause my engine to run lean and throw lean codes (SES). For less than $7.00 I replaced both and it made a world of difference.