TM 5-3895-346-14
VALVE AND INJECTOR OPERATING MECHANISM
ENGINE OVERHAUL
VALVE AND INJECTOR OPERATING MECHANISM
Three rocker arms are provided for each cylinder; the two outer arms operate the exhaust valves and the
center arm operates the fuel injector.
Each set of three rocker arms pivots on a shaft supported by two brackets. A single bolt secures each bracket
to the top of the cylinder head. Removal of the two bracket bolts permits the rocker arm assembly for one
cylinder to be raised, providing easy access to the fuel injector and the exhaust valve springs.
The rocker arms are operated by a camshaft through cam followers and short push rods extending through the
cylinder head (Fig. 1).
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 retain the cam followers in place and to align the cam follower
rollers with the camshaft lobes. Figure 1. Valve and Injector Operating Mechanism A coil spring, inside of
each cam follower, maintains a predetermined load on the cam follower to ensure contact of the cam roller on
the camshaft lobe at all times.
Lubrication
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.
Overflow oil from the rocker arms lubricates the exhaust valves 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.
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
grooves in the camshaft bushing bores in the
cylinder block.
Service
The following service operations may be
performed on the valve and injector operating
mechanism without removing the cylinder head:
1.
Adjust valve clearance.
2.
Replace a valve spring.
3.
Replace a rocker arm.
4.
Replace a rocker arm shaft or bracket.
5.
Replace a fuel injector.
Figure 1. Valve and Injector Operating Mechanism
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