Positive Crankcase Ventilation: Description and Operation

This system is used to eliminate emission of residual fumes and vapors from the crankcase by directing these fumes back through the combustion chamber.
When the engine is running, air is drawn by manifold vacuum from the air cleaner through a hose, to the crankcase inlet air cleaner. From the crankcase inlet air cleaner, the air mixes with vapors in the rocker arm chamber and crankcase, and then drawn up through the PCV valve in the cylinder head cover to a hose connected to either the intake manifold or carburetor hose.