[T]he valves, which open and close to let the air-fuel mixture in and out of the cylinders, are above the camshaft, which is in the engine block. The camshaft activates pushrods that move up and ...

IN THE usual auttmobile poppet valve the poppet or mushroom valves are lifted from their seats by cams and reseated by springs. In a four·cycle motor, the valves in each cylinder are Oiened and ...