DETROIT DIESEL 53
1.2.1
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 rocker arm assemblies pivots on a shaft supported by two brackets. A single bolt secures each bracket to the
top of the cylinder head. Consequently, the removal of two bracket bolts permits the rocker arm assembly for one
cylinder to be raised, providing easy access to the fuel injector and valve springs.
The rocker arms are operated by the 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 keep the follower rollers in line with the cams and serves as a retainer during assembly
and disassembly.
A coil spring, located inside of each cam follower, is held in place in the cylinder head by a spring seat and spring seat
retainer.
Several operations may be performed on the valve mechanism without removing the cylinder head from the cylinder
block, while the head must be removed for certain other operations. The operations NOT requiring removal of the
cylinder head are:
1.
Adjusting valve clearance.
2.
Removing and installing a valve spring.
3.
Removing and installing a rocker arm.
4.
Removing and installing a rocker arm shaft or shaft bracket.
5.
Removing and installing an injector.
It is also possible, if occasion requires, to remove or replace a push rod, push rod spring, spring seats or cam follower
without removing the cylinder head. These parts, however, are more easily changed from the lower side of the cylinder
head when the head is off the engine. Both methods are covered in this Section.
To remove and install valves, valve guides, valve seat inserts and to recondition valves and valve seats, the cylinder
head must be removed. Exhaust valves, guides and inserts are covered in Section 1.2.2.
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 oil passages in the cylinder block. Oil from this
Fig. 1 - Injector Operating Mechanism (In-Line Engine Shown)
Fig. 2 - Cam Follower and Guide Location
July, 1972
SEC. 1.2.1
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