D 250 Pickup L6-359 5.9L DSL (1992)
Camshaft: Description and Operation
The camshaft is gear driven from the crankshaft. A replaceable bushing is used for the front journal to carry the side loading from the accessory drive.
The remainder of the journals operate In cast iron bores in the cylinder block
The camshaft has lobes to operate the intake and exhaust valves and a special lobe to drive the lift pump. The valve lobes contact "mushroom" shaped
valve tappets which operate the push rods. The operating arm of the lift pump. rides directly on the special lobe on the camshaft. The profile of the cam
lobes is the same for all B Series engines.
The center line of the tappet is slightly offset from the center line of the cam lobe. This design feature and the slightly convex surface of the tappet causes
the tappet to rotate as it is lifted by the cam.
