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 TM 55-1905-220-14-5
3-90.1. VALVE AND INJECTOR OPERATING MECHANISM - MAINTENANCE INSTRUCTIONS.
a. Three rocker arms are provided for each cylinder; the two outer arms operate the exhaust valves and the center
arm operates the fuel injector.
b. Each set of three rocker arm assemblies pivot on a shaft supported by two brackets. A single bolt secures each
bracket to the top of the cylinder head. The removal of the two bracket bolts permit the rocker arm assembly for one
cylinder to be raised, providing easy access to the fuel injector and the exhaust valve springs.
c. The rocker arms are operated by a camshaft through cam followers and short push rods extending through each
cylinder head.
d. Contact between each cam follower and the camshaft is done by a hardened roller having a pressed-in bushing,
which runs on a pin in the lower end of the cam follower. Each cam follower operates in a bore in the cylinder head. A
guide for each set of three cam followers is attached to the bottom of the cylinder head to keep the cam follower rollers in
line with the cams and to serve as a retainer during assembly and disassembly of the cylinder head.
e. A coil spring inside each cam follower is held in place in the cylinder head by a spring seat and spring seat
retainer.
f. The valve and injector operating mechanism is lubricated by oil from a longitudinal oil passage on the camshaft
side of the cylinder head, which connects with the main oil gallery in the cylinder block. Oil from this passage flows
through drilled passages in the rocker shaft bracket bolts, to the passages in the rocker arm shaft to lubricate the rocker
arms.
g. Overflow oil from the rocker arms lubricate the exhaust valves, valve bridges and cam followers. The oil then
drains from the top deck of the cylinder head through oil holes in the cam followers, into the camshaft pockets in the
cylinder block and back to the oil pan.
h. The cam follower rollers are lubricated with oil from the cam followers; oil picked up by the camshaft lobes and
by oil emitted under pressure from milled slots in the camshaft intermediate bearings.
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