280 Models With Vent Valve

System consists of a sealed oil filler cap, a vent valve in camshaft housing, and a hose connecting either the air filter, or purge port below throttle valve to cylinder head cover. The blow-by gases and crankcase vapors are routed through an oil separator in cylinder head cover to vent valve, continuing through to air filter, or purge port and into combustion chamber.

NOTE: Use only cylinder head covers with oil protection ribs.

At idle and low speeds, engine vacuum draws clean air from the air filter which picks up blow-by gases and vapors via the vent valve, drawing them into the intake manifold to be burned in combustion chamber. Depending on intake vacuum, the valve will be pulled or pressed and change the amount of blow-by gases taken in from the crankcase. At higher speeds, blow-by gases and crankcase vapors flow from cylinder head cover into air filter and into engine to be burned in combustion chamber.