Positive Crankcase Ventilation Valve: Description and Operation

Positive Crankcase Ventilation System:

PURPOSE
The Positive Crankcase Ventilation System prevents air pollution caused by blow-by gasses being vented to the atmosphere.
The valve is threaded into the intake manifold.

OPERATION
At part throttle, blow-by gas and filtered air from the filter in the air cleaner are drawn by strong vacuum into the intake manifold through a connecting hose and PCV valve. At wide open throttle, part of the blow-by gas flows into the air cleaner through a connecting hose and is then drawn into the engine through the throttle valve. This compensates for lowered manifold vacuum at high engine speeds.