Positive Crankcase Ventilation: Description and Operation

Fig. 3 PCV Valve:

Fig. 4 Fresh Air Hose:

Intake manifold vacuum removes crankcase vapors and piston blow-by from the engine. The emissions pass through the PCV valve into the intake manifold plenums (Fig. 3). The vapors become part of the calibrated air-fuel mixture, are burned and expelled with the exhaust gases. The air cleaner supplies make up air when the engine does not have enough vapor or blow-by gases. In this system, fresh air enters the crankcase through the left valve cover (Fig. 4).