When do you know when not to use a pcv valve.
I've been told that pcv valves should not be used on a performance engine. Another person told me that pcv valves are free horsepower.
Is a pcv valve used a street car only?. Do camshaft duration, piston rings, and torque converter stall have anything to do with it?.

Hey Big Block,
The only time to not use PCV is on an all out race only car.In a drag car most of its use is at wide open throttle (WOT),there fore no vacuum.Although in this case header scavenger kits should be used because they create vacuum at WOT to act as PCV.

The PCV has many advantages; it collects the crank case smoke-smell and burns it through the engine,also as the engine warms up each time you run it,there is condensate formed inside the crank case,the reason to run 180 thermostat or hotter is to turn this condensate into steam and also draw it through the PCV - engine and burn it,other wise sludge occurs quicker. The biggie I like is the engine leaks much less oil when system is evacuated properly.

The last thing is even with large cams the vacuum rises every time you lift the throttle making the PCV function, mabe not as well as stock cam,but unhook it and see how much oil it starts leaking.

Larry

Larry,

Thank you for explaining why pcv valves are needed!!!.

Matt.

And they are not created equal! I recently swapped a new one with a 90 elbow for the one that came with the car. this is a mildly hot 427 idles at 14" of vacuum. HUGE differece in idle quality. Then I got a 1969 427/435 HP PCV and had another, more subtle change.

Crazy little things are more complicated than I thought. There is a code on the bottom of them, ID'ing the innards.

Use a stnadard motor part V158(vette) or V178(std GM with 90 elbow).

427TRI is correct. Not all PCV valves are created equal. Different engines need different valves. I look at the hi-po factory versions to determine what would work best for my engine. Also, buy good quality parts, some of the stuff out there is junk.

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