HOW THE OEM PCV VALVE WORKS

 

BELOW, VALVE IS CLOSED WHEN ENGINE IS NOT RUNNING BELOW, IN NORMAL RUNNING USUALLY AT CRUISE, PART OPEN

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ABOVE, AT IDLE, VALVE OPENING IS SMALL. AN OLD ENGINE WILL HAVE POSITIVE PRESSURE IN THE CRANKCASE CAUSING FUMES TO BE EXPELED AT ANY WEAK OPENING. ABOVE, AT 3/4 THROTTLE, THE VALVE IS WIDE OPEN. NOTICE VERY LITTLE SPACE FOR GASSES TO PASS THRU. WORSE YET, VALVE TENDS TO CLOSE AT FULL THROTTLE MAKING MATTERS WORSE.

      

                   BESIDES THE FACT THAT THIS VALVE GETS CLOGGED BY SOOT IN 

                   TIME, IT ALSO WEARS. THE INTAKE MANIFOLD CONTROLS THIS

                   VALVE AND NEVER KNOWS IF THERE IS TOO MUCH PRESSURE

                   (BLOWBY) IN THE CRANKCASE. IT IS OUTDATED WHEN THE

                   PISTON RINGS WEAR. THIS SYSTEM HAS EXISTED SINCE 1958

                   WITHOUT AND CHANGES EXCEPT TO MAKE THE ORIFACE BIGGER.