I need to match a PCV valve with my roller cam - Team Camaro Tech
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post #1 of 11 (permalink) Old Aug 24th, 14, 08:24 PM Thread Starter
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Mark
 
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I need to match a PCV valve with my roller cam

I'd like to change my stock 70 Z28 PCV valve CV746C (K), to one that matches my idle vacuum reading with my roller cam that produces 11-12" at idle. I read that the 69 Z/28 part no 6484699 would be a good choice. What's the idle vacuum reading for a 69 Z/28? Is there a PCV cross reference chart available for all brands with engine vacuum specs.

Mark 70 Z28 M22 3.73 Z21 Z87 - Lunati 20120121 Roller Cam

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post #2 of 11 (permalink) Old Aug 24th, 14, 08:29 PM
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Rick
 
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Re: I need to match a PCV valve with my roller cam

The CV746C is the same as a '69 Z28 and LS6 if I'm not mistaken.
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post #3 of 11 (permalink) Old Aug 24th, 14, 09:00 PM Thread Starter
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Re: I need to match a PCV valve with my roller cam

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Originally Posted by rp930 View Post
The CV746C is the same as a '69 Z28 and LS6 if I'm not mistaken.
Your correct, just checked the parts book. Part no 6484525.

Mark 70 Z28 M22 3.73 Z21 Z87 - Lunati 20120121 Roller Cam

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post #4 of 11 (permalink) Old Oct 23rd, 14, 08:24 PM Thread Starter
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Re: I need to match a PCV valve with my roller cam

I bought one of these hallow fixed orifice pcv valves and it fixed my oil consumption problem. I tested the vacuum at the oil dipstick tube and with the stock 70 Z28 pcv and got 6" of vacuum when it should be between 1-3". The reading with the new pcv is 2".



Testing: http://www.underhoodservice.com/tech...v-inspections/ Go to heading Testing a PVC Valve

Mark 70 Z28 M22 3.73 Z21 Z87 - Lunati 20120121 Roller Cam

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post #5 of 11 (permalink) Old Oct 27th, 14, 04:41 PM
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Re: I need to match a PCV valve with my roller cam

auto zone does not show this pcv . where did you get it , pt # and how much? thanks
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post #6 of 11 (permalink) Old Oct 27th, 14, 05:45 PM
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Re: I need to match a PCV valve with my roller cam

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Originally Posted by jerrys 67 View Post
auto zone does not show this pcv . where did you get it , pt # and how much? thanks
Part no 6484525, this is a gm part number. Use this part number to interchange , if still no luck, go to Napa. If still no luck use the CV 746C number. This was an AC part number.

Probably under 10$.

Autozone could not find it because they probably need to know what color your car was.

Don
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post #7 of 11 (permalink) Old Oct 27th, 14, 06:12 PM
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Re: I need to match a PCV valve with my roller cam

so that im educamacated on this - what is the purpose of changing the PCV valve and the vacumn reading? How or what determined that you needed to change this??

Eddie M
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post #8 of 11 (permalink) Old Oct 27th, 14, 08:55 PM Thread Starter
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Re: I need to match a PCV valve with my roller cam

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Originally Posted by enio45 View Post
so that im educamacated on this - what is the purpose of changing the PCV valve and the vacumn reading? How or what determined that you needed to change this??
Oil consumption. My rebuilt roller motor has a vacuum reading of 6" in the crankcase with the stock 70 Z28 PCV valve.
For a properly working PCV you should only have a reading between 1-3" at idle. GM used this hallowed out PCV on
many many cars and trucks that consumed oil. They no longer sell the PCV 12572717. Mine was $10 in Canada at
Carquest. Part # 76-2698.

Mark 70 Z28 M22 3.73 Z21 Z87 - Lunati 20120121 Roller Cam

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post #9 of 11 (permalink) Old Oct 28th, 14, 05:24 AM
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Re: I need to match a PCV valve with my roller cam

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Originally Posted by COPO View Post
Oil consumption. My rebuilt roller motor has a vacuum reading of 6" in the crankcase with the stock 70 Z28 PCV valve.
For a properly working PCV you should only have a reading between 1-3" at idle.
Where do you take that reading? Dipstick tube? Or at the PCV?

Edit: Never mind. I saw above where you said at the dipstick.
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post #10 of 11 (permalink) Old Oct 29th, 14, 04:23 AM
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Re: I need to match a PCV valve with my roller cam

Quote:
Originally Posted by enio45 View Post
so that im educamacated on this - what is the purpose of changing the PCV valve and the vacumn reading? How or what determined that you needed to change this??

The way a variable valve PCV works is that engine vacuum actually pulls the pintle valve closed. It tries to maintain the same crankcase vacuum under all conditions. So, high engine vacuum (low load, less chance of blow-by) the valve is more closed to limit both the "vacuum leak" at the PCV and crankcase vacuum. Low engine vacuum, (high load, more chance of blow-by) the valve is more open to try to maintain that crankcase vacuum.

They are made with different springs in them depending on application. If you use a PCV made for a big solid lift cam engine that typically makes low idle vacuum in an engine that makes a higher amount of engine vacuum, then the valve will be a lot more open at low load and idle than it should be resulting in a large "vacuum leak" and too much negative crankcase vacuum. Likewise doing the opposite (high vac engine PCV in a low vac engine) will result in a valve that doesn't create enough crankcase vacuum at low load because the valve will be pulled closed.

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post #11 of 11 (permalink) Old Oct 29th, 14, 06:18 AM Thread Starter
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Re: I need to match a PCV valve with my roller cam

Quote:
Originally Posted by trland View Post
Where do you take that reading? Dipstick tube? Or at the PCV?

Edit: Never mind. I saw above where you said at the dipstick.
And put duct tape over the grommet on the pass side or your reading will be zero.

Mark 70 Z28 M22 3.73 Z21 Z87 - Lunati 20120121 Roller Cam

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