| |
| 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 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 action provides longer service life for the valves.
When cam follower (7) moves downward, valve spring (4) closes the valve.
Engine Timing Actuator - The G3500 TA supports an engine timing actuator control system. The system is electronically controlled and hydraulically actuated. The system rotates the camshaft position to change the valve opening and closing profiles.
The advantages over non-equipped engines are:
- Improved engine starting
- The ability to manage load at a lower RPM
- Management of detonation independent of ignition timing adjustments
An oil control solenoid valve controls oil flow into passages which allow rotation of the camshaft independent of the cam gear, in both the clockwise and the counterclockwise direction.
The oil control solenoid valve will open to allow engine oil to enter the engine timing actuator rotor cavity, which is connected to the camshaft. The camshaft position can be advanced between 0 and 20 degrees of the current position.
Deactivation of the oil control solenoid valve will stop the flow of engine oil to the cavity. This action will allow a torsion spring to return the rotor and camshaft to a non-advanced position.
Refer to Troubleshooting, Solenoid Valve - Test for information on the oil control solenoid valve.