Carbureted Engine

Fig. 8 Closed crankcase ventilation system.:

Fig. 9 Typical closed crankcase ventilation system.:

Civic, CRX, Prelude & 1986-88 Accord
During normal operation, blow-by gasses are evacuated from the engine through a liquid/vapor separator mounted on the crankcase. Manifold vacuum is applied to the liquid/vapor separator through a PCV valve. Ventilating air is drawn into the engine through a separate filter in the air cleaner that is connected to the valve cover by a hose, Figs. 8 through 10. The air is drawn down into the crankcase through the oil return passages by manifold vacuum, where it mixes with the blow-by gasses, and the blow-by gasses are drawn into the intake stream and burned during the normal combustion process.
During low vacuum, wide open throttle operation air flow through the engine is reversed. Vacuum created in the air cleaner overcomes manifold vacuum, and the blow-by gasses are drawn from the valve cover into the air cleaner.