Positive Crankcase Ventilation: Description and Operation

Fig. 9 PCV system:

The PCV system, Fig. 9, forces blow-by gas, generated in the engine crankcase back into the intake manifold. It is then delivered to the combustion chamber along with the air/fuel mixture. The PCV system consists of a head cover baffle plate, a regulating orifice, hose connections and a hose.
The regulating orifice controls blow-by gas suction. Under normal operating conditions, blow-by gas passing between the piston and the cylinder wall is mixed in the engine with fresh air from the air cleaner. The baffle plate, mounted in the head cover, separates oil particles from the blow-by gas. The blow-by gas is then drawn through the regulating orifice into the intake manifold to be reburned in the combustion chamber. With the engine operating at maximum speed, intake manifold negative pressure will not be sufficient to handle all of the blow-by gas. Some of the gas will be drawn into the air cleaner, through the rear end of the head cover.