Air Suction System

On 1977 3K-C engine, the system draws in fresh air from air suction valve into exhaust port. Negative pressure caused by valve overlap and pulsation in exhaust port makes this possible. When vacuum acts on air suction valve, valve opens and fresh air is drawn into exhaust ports. Positive pressure will cause air suction valve to close, preventing backfire from traveling back up into valve.

On 1978-79 models, the suction valve responds to exhaust system pressure and atmospheric pressure to control intake of air into the exhaust ports. This system accomplishes the same purpose as the air injection system. Pulsations created by the combustion process open and close the air suction valve. When the pulsation is negative (atmospheric pressure is greater than exhaust system pressure) the valve opens and fresh air is drawn in. When exhaust pressure is positive, the valve closes and no air is drawn in.