The crankcase ventilation system is used to provide more complete scavenging of the crankcase vapors. Fresh air from the air cleaner is supplied to the crankcase, mixed with blow-by gases and then passed through a crankcase ventilation valve (1) into the intake manifold.

The primary control is through the crankcase ventilation valve which meters the flow at a rate depending on manifold vacuum

To Maintain idle quality, the valve (1) restricts the flow when intake manifold vacuum is high. Whenever abnormal operating condition arise, the system allows excessive amounts of blow-by gases to back flow through the crankcase vent tube into the rear air duct to be consumed by normal combustion