BOOT 5N4432 - Caterpillar

The valve system components control the flow of the inlet air and of the fuel into the cylinders and the flow of exhaust gas out of the cylinders during engine operation.
Illustration 1 g00813876
(1) Rocker arm
(2) Valve bridge
(3) Valve rotator
(4) Valve spring
(5) Pushrod
(6) Valve
(7) Cam follower
(8) Camshaft lobe The crankshaft gear drives the camshaft gears through idler gears. The camshafts must be timed to the crankshaft in order to get the correct relation between the movement of the piston and movement of the valves.The camshafts have two camshaft lobes (8) for each cylinder. As the camshaft turns, the camshaft lobe causes cam follower (7) and pushrod (5) to move up and down.The pushrod moves rocker arm (1). Movement of the rocker arm causes valve bridge (2) to move up and down on a dowel in the cylinder head. This movement operates valves (6). The valve bridge enables one rocker arm to operate two valves simultaneously. There are two inlet valves and two exhaust valves for each cylinder.Valve rotator (3) turns the valve during engine operation. The rotation of the valves keeps the deposit of carbon on the valves to a minimum. This provides longer service life for the valves.When cam follower (7) moves downward, valve spring (4) closes the valve.