PCV valve research...

[Roadster]

Now to be even more
Here is a link to the AC DELCO catalog which shows 3 different PCV valves for the ZR-1 1990-1995. CV913C is shown and listed for the "Right" and #19303069 is listed for both "Left & Right".
So is the "Right" really the driver's side and the "Left" really the passenger side??? Hmmmm to be determined!!!

http://parts-catalog.acdelco.com/cat...log_search.php

You will need to enter the info to get results....

[A26B]

The CV913C & CV895C may have an internal difference, specifically "crack" pressure. This could be determined by securing the valve, attaching a vacuum pump to the top connection & determining the vacuum needed to raise the valve off seat, i.e. "crack pressure.

[TealZR1]

I researched this "taller" PCV Valve a while back and could not find the exact fit. So I soaked my original in a degreaser and placed back on thinking my idle would go down to 7500 rpm. Didn't happen so pulled the plenum and found the famous hose disconnection and repaired that and thus bringing idle down to 7500! Car has 61K miles.

Really like the ZR1 car but seems to have the old Porsche 928 dilemma where parts were somewhat scarce & expensive thus driving the price down. I owned a Porsche 928 years ago and the "older" gent owner told me when I bought it from him as a young 28 year old - "you are buying a $75K Super Car for only $15K and expect your monthly payment being repairs, parts, etc to keep it running" Really fortunate we have this website and self repairing of my ZR1.
Enjoy the ZR1 performance and keep em running top notch!

[Roadster]

Originally Posted by A26B

The CV913C & CV895C may have an internal difference, specifically "crack" pressure. This could be determined by securing the valve, attaching a vacuum pump to the top connection & determining the vacuum needed to raise the valve off seat, i.e. "crack pressure.

Don't know if I did this correctly, but I did hook up the vacuum pump to the top "stem" connection and could not get any reading until I placed my thumb on the bottom. On both the CV913C and the short V291 valve I could get a reading as high as 23-24 in. and of course it would hold until I released my thumb. So there wasn't a way to determine when or if the valve would lift off the seat doing it the way I did. I couldn't find any other info on "crack pressure". So if you could elaborate more I could give it another try.

Originally Posted by TealZR1

I researched this "taller" PCV Valve a while back and could not find the exact fit. So I soaked my original in a degreaser and placed back on thinking my idle would go down to 7500 rpm. Didn't happen so pulled the plenum and found the famous hose disconnection and repaired that and thus bringing idle down to 7500! Car has 61K miles.

Really like the ZR1 car but seems to have the old Porsche 928 dilemma where parts were somewhat scarce & expensive thus driving the price down. I owned a Porsche 928 years ago and the "older" gent owner told me when I bought it from him as a young 28 year old - "you are buying a $75K Super Car for only $15K and expect your monthly payment being repairs, parts, etc to keep it running" Really fortunate we have this website and self repairing of my ZR1.
Enjoy the ZR1 performance and keep em running top notch!

I also gave it thought about soaking, but have read and seen others using brake kleen or carb cleaner to clean out the valve.
And are you meaning to bring down the idle to 750r's???

[A26B]

Originally Posted by Roadster

Don't know if I did this correctly, but I did hook up the vacuum pump to the top "stem" connection and could not get any reading until I placed my thumb on the bottom. On both the CV913C and the short V291 valve I could get a reading as high as 23-24 in. and of course it would hold until I released my thumb. So there wasn't a way to determine when or if the valve would lift off the seat doing it the way I did. I couldn't find any other info on "crack pressure". So if you could elaborate more I could give it another try.

Crack pressure is a terminology used in industrial safety valve testing specs, simply meaning when the valve comes off seat or begins to leak past the valve seal.

Imagine a check valve, which is the type of valve the subject PCV valve is. The PCV valve has a moveable valve that is weighted for specific conditions such as the LH LT5 valve (tall one), being one of 2 valves in the system and staged for opening under slightly different conditions from the RH valve.

If both PCV valves had the same crack pressure, subject to the same vacuum pressure and same crankcase pressure, then there would be no purpose served by having two different valves side by side in the system.

I suggested vacuum testing from the top connection over pressure testing at the bottom/inlet side because most of us own a hand vacuum tester that may be able to measure the anticipated low pressure without any special rigging.

I would approach testing in the following manner.

1. Secure the valve to prevent movement during testing. Position vertically with bottom open to atmosphere.
2. connect hand vacuum hose to top connector.
3. gradually apply vacuum in small increments & verify vacuum holding before increasing to next increment. When vacuum no longer holds, crack pressure is at point above last increment held & point leakage observed.

FYI: None of this may be achievable to a definitive end. The 895 valve may work even if it's not the same as Lotus spec'd 913 valve, just not exactly as designed. Effect may be inconsequential to the normal ZR-1 driver, and it may simply result in slightly more oil consumption that goes unnoticed.

[Roadster]

Originally Posted by A26B

I would approach testing in the following manner.

1. Secure the valve to prevent movement during testing. Position vertically with bottom open to atmosphere.
2. connect hand vacuum hose to top connector.
3. gradually apply vacuum in small increments & verify vacuum holding before increasing to next increment. When vacuum no longer holds, crack pressure is at point above last increment held & point leakage observed.

Thanks for the response, always good to learn something new. I did follow your steps, but before I was continuously pumping the vacuum handle which resulted in the 23-24 inch readings.
Did it again a few minutes ago exactly as stated in #3, but the gauge would not register until I closed off the bottom of the valve with my thumb. Which resulted in the same readings as last night. When I have the valve closed, the pump works fine, with the bottom opened, again not registering.

An interesting discussion.....

[Roadster]

Just got back from getting the 94 inspected. No emissions needed as I was just under 5000 miles....

FYI, spoke to the parts person and he verified that both CV913C & CV895C PCV valves are discontinued from GM. Then again most of you may already have known that. They just are very hard to find. Was lucky to get some 895's on the bay, but no luck on the 913's.

[Roadster]

Just received delivery today of an original NOS CV913C "double hump" PCV valve. I was notified by a member that he had found some 913 valves. I made the call, and between the two of us, we now have NOS 913's. Feeling very thankful for the info which led to the purchase. Thank you again sir, it is very much appreciated.
Unfortunately the source is now out of 913's.
In the pic, you will notice that once again the packaging is the old style AC box from many years ago. Also interesting to note is that this NOS 913 does not have "AC ROCHESTER" stamped on the valve, rather it has
"AC SPARK PLUG" stamped on it instead.


the new NOS valve is on the left, the "original" or I think original from my 94, unless it had been replaced years ago on the right....

[Roadster]

Did a little more research and found a listing by Corvette Central for a LT1
92-96 Corvette PCV valve. Sent an email about the length and it is 1 7/8".
Which is the correct size and their current listing shows it is a CV895C, but number is not shown in the pic. Also has the application guide which is including ZR-1's.

http://www.ebay.com/itm/1992-1996-Co...777325?vxp=mtr

Corvette Central #: 304577
Original GM #: 25095452

So another source for some 895 "double hump" valves, just in case. And I now have some extras if anyone has a problem with locating one when ready...

[-=Jeff=-]

But is the function of each game Benin the correct size the same? I have a feeling they are different despite the size


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