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I've spent hours searching on this topic and have a better grasp on crankcase ventilation.
The "gray" area remaining is: Do different engines require different "level"(calibration) of PCV valve?
The previous posts indicate there are different levels of vacuum to activate the valve (allow crankcase gases to go back thru intake) but the aftermarket companies sell breathers with some "generic" PCV valve (ie. Spectre, Billet Zoops etc.) in them. Also, the guy at the auto parts store laughed at me when I suggested there might be different valve opening pressures with different valves. He said, "A PCV valve is a PCV valve". So, are there different calibrated valves or is it basically one size fits all?
Thanks in advance!
John
 

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Go back to the parts store and have the guy that laughed look up a PCV valve for a '69 427ci Corvette and one for a '69 307 out of a Camaro... There will be 2 different part numbers.

The best I can tell you is the aftermarket tend to lean toward the performance side and if they offer a one part fits all, it will be metered for a low idle vacuum lumpy cam engine.
 

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Also, the guy at the auto parts store laughed at me when I suggested there might be different valve opening pressures with different valves. He said, "A PCV valve is a PCV valve".
Time to find another parts counter guy.

Do you know what your vacuum (Hg) is at idle? Let us know and we'll pick you an AC Delco number that works with that Hg. As stated above, it could be anything from a 2-bbl 307 to an 427 L-88. The 307 would pull about 18 hg vacuum at idle and the L-88 would pull about 8.
 

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Recent experience with this, I was using an unknown PVC valve just because it fit the grommet. Oil vapor was pushing past the grommets, running down the valve cover fins. I dont think it was opening when it was supposed to. Switched to a correctly rated one for my engine, no more oil vapor.


Sent from my iPhone using Autoguide
 

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what would a good PCV number be for a mechanical cam with 5-7 inches of vacuum be?
 

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Thanks, Guys!
 
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