A crankcase ventilation system is used to provide scavenging of the crankcase vapors. Blow-by gases are passed through a crankcase ventilation oil/air separator into the air cleaner outlet resonator. The oil/air separator is inside the valve cover and allows any scavenged oil to be returned to the crankcase.

The only flow through the oil and air separator is the combustion blow-by, as there is no fresh air inlet to the crankcase. The primary flow of blow-by into the separator is through the openings inside the valve rocker arm cover. The oil and air separator causes oil, which may be suspended in the blow-by gases, to be separated and to drain back to the crankcase. The blow-by gases are then drawn into the air cleaner outlet resonator by normal engine vacuum and burned in the combustion process.