Crankcase Ventilation Systems: Operation

At part throttle, blow-by gas from the crankcase is drawn into the intake manifold through the connecting hose of cylinders 2 and 4 rocker arm cover and the PCV valve. At the same time, fresh air is drawn into the crankcase through the air cleaner and connecting hose of cylinders 1 and 3 rocker arm cover, and routed to the intake manifold along with the blow-by gas.

At wide open throttle, when intake manifold vacuum is low, the blow-by is directed into the air cleaner through cylinders 1 and 3 rocker arm cover connecting hose, and is drawn into the carburetor.