09-17-2007, 08:44 AM
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CC Member
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Join Date: Sep 2002
Location: Hickory,
NC
Cobra Make, Engine: ERA 427SC w/427so, ERA GT #2002
Posts: 1,106
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Not Ranked
A PCV valve is a win-win deal. They allow nasty vapors from being evacuated from the crankcase and burned, plus they keep oil vapors off your engine. The rattling you hear is the valve is shaked back and forth is the valve being moved in the totally closed position for WOT operation to the slightly opened one for idle. It's mostly opened at part throttle.
Installing a PCV valve may require rejetting to a fatter jet if you're running a carburetor(s). Most of the "vapors" pulled from the crankcase is air (O2, Nitrogen, etc.), thus creating a lean condition at part throttle. Others include water vapor, CO2, CO, acid and HC. The best thing to have in a crancase is low pressure (vacuum), which is accomplished with a PCV valve, except at WOT operation. So, unless you're running a race car, it's best to run a PCV system.
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Tom
"If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough HORSEPOWER." Mark Donohue
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