Positive Crankcase Ventilation: Description and Operation

Fig. 87 PCV System:

The purpose of the positive crankcase ventilation system is to prevent crankcase vapors from escaping into the atmosphere. Hoses link the crankcase to the air cleaner and the calibrated orifice in the intake system. During part throttle operation the crankcase is ventilated through the vapor separator and the calibrated orifice in the intake manifold to the idle air channel. Blowby gases are drawn from the crankcase through the calibrated orifice into the intake manifold and burned. During partial load to full throttle the gases flow through the crankcase to the valve cover, past the oil separator and into the air cleaner where they are introduced into the intake system.