K Series Positive Crankcase Ventilation System
Low blow-by gas flow. High manifold vacuum. Blow-by gases are drawn out of the cam cover through the PCV restricted orifice. Volume of gas drawn out exceeds blow-by gas flow (crankcase pressure below atmospheric) so additional fresh air is drawn in from inside the air filter via the breather.
High blow-by gas flow. Low manifold vacuum. Less blow-by gas is drawn out of the cam cover through the PCV restricted orifice due to the reduced manifold vacuum. More blow-by gasses are produced, exceeding the volume drawn out into the manifold (crankcase pressure above atmospheric) so additional blow-by gasses flow back through the breather to be drawn into the manifold and consumed by the engine.