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Old 09-12-2005, 07:00 PM
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PCV Question

Hey Guys,
I've got a question regarding a PCV valve. I'm running a 327 with a Holley 600 on an old Edelbrock Torker single plane manifold. I have an Edelbrock Performer RPM Cam installed.
I know that the manifold and the cam are not a good match, but I have a hood clearance problem and cannot install the proper Edelbrock RPM Dual plane intake at this time.

My question is: Should the PCV Valve be hooked up to full manifold vacuum or should it be just vented thru the air cleaner? When I attach the hose from the PCV to the full vacuum port on the manifold, it acts like a vacuum leak and the idle picks up about 300 rpm. I cannot re-set the idle to normal with the PCV hooked up, but when I pinch off the hose, the idle drops back to an acceptable speed. I have about 16 Inches Hg at that port at idle.


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Old 09-12-2005, 07:57 PM
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PCV valve needs full manifold vacuum to work properly. As for the vacuum leak problem you must have a bad PCV valve. you must also have a crank case breather on the other valve cover so pressure doesn't build up in the engine.
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Old 09-13-2005, 12:24 PM
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I think it should be hooked up to both, one side to the manifold, the other side to the air cleaner.

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Old 09-13-2005, 01:34 PM
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You really need a PCV system on your engine.

2 things come to mind on the RPM increase.
First, the carb idle mixture is so rich that the increase in air from the pcv is leaning it out some and letting the speed come up.
Second, the oil is fuel saturated and the pcv is adding even more fuel to the intake causing the rpm to go up.

Check the oil for gas smell or try to light a few drops with a match.
Not sure why you can't lower the base idle speed. Are the secondaires cracked open some? Is the choke fast idle cam still partially activated?
The idle speed screw should be able to close the primaries completely so the engine dies. If not, something is wrong.

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Old 09-13-2005, 04:54 PM
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The PCV is a calculated leak. Your engine should run fine
with it hooked up properly. Properly means manifold vacuum
to the valve, and atmosphere to the engine, through either
the air filter, or a filter/oil filler on the oppisite head. What
this does is two fold, vent the crank case, which is a good
thing, your car won't smell like it's burning oil while sitting
at a stoplight, and draws off the water vapor that builds
up in the oil, which happens every time you shut the car off
for the night. Condensation in the oil is a bad thing...
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