Interference and Timing By: Stuart Johns

Interference Engine “When an engine is an ‘interference engine’ the pistons and valves are so close together that if the valves were to stop moving and the crankshaft kept spinning they would crash into the piston” This can potentially break the valve, push rod and pistons if not properly maintained

Camshaft Timing Intake valve opens as piston starts moving downward and closes at the bottom (dead top center) Exhaust valve opens as piston ascends, and closes as the piston reaches the top (bottom dead center)

Crankshaft Timing A crankshaft changes a piston’s up and down to a continuous circular motion

Timing The camshaft and crankshaft need to be timed so that as the crankshaft pulls the piston down the camshaft intake valve is opening, or as the piston is pushed up the exhaust valve opens. At high RPM the camshaft needs to be offset so that both intake and exhaust valves are open, otherwise the airflow will stop

References ine.htm haft_testrender.jpg