DETROIT DIESEL 53
VALVE AND INJECTOR OPERATING MECHANISM
Three rocker arms are provided for each cylinder; the
1. Adjusting valve clearance.
two outer arms operate the exhaust valves and the
center arm operates tie fuel injector.
2. Removing and installing a valve spring.
Each set of rocker arm assemblies pivots on a shaft
3. Removing and installing a rocker arm.
supported by two brackets. A single bolt secures each
bracket to the top of the cylinder head. Consequently,
4. Removing and installing a rocker arm shaft or shaft
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.
5. Removing and installing an injector.
The rocker arms are operated by the camshaft through
It is also possible, if occasion requires, to remove or
cam followers and short push rods extending through
replace a push rod, push rod spring, spring seats or cam
the cylinder head (Fig. 1).
follower without removing the cylinder head. These
parts, however, are more easily changed from the lower
Each cam follower operates in a bore in the cylinder
side of the cylinder head when the head is off the
head. A guide for each set of three cam followers is
engine. Both methods are covered in this Section.
attached to the bottom of the cylinder head to keep the
follower rollers in line with the cams and serves as a
To remove and install valves, valve guides, valve seat
retainer during assembly and disassembly.
inserts and to recondition valves and valve seats, the
cylinder head must be removed. Exhaust valves,
A coil spring, located inside of each cam follower, is
guides and inserts are covered in Section 1.2.2.
held in place in the cylinder head by a spring seat and
spring seat retainer.
Several operations may be performed on the valve
The valve and injector operating mechanism is
mechanism without removing the cylinder head from the
lubricated by oil from a longitudinal oil passage, on the
cylinder block, while the head must be removed for
camshaft side of the cylinder head, which connects with
certain other operations. The operations NOT requiring
oil passages in the cylinder block. Oil from this
removal of the cylinder head are:
Fig. 1. - Injector Operating Mechanism (Shown)
Fig 2. - Cam follower and Guide Location
1972 General Motors Corp
SEC 1.2.1 Page 1