Valvetrain

A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine.^[1] The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) into the combustion chamber, while the exhaust valves control the flow of spent exhaust gasses out of the combustion chamber once combustion is completed.^[2]