TM 5-3895-346-14
ENGINE OVERHAUL
VALVE OPERATING MECHANISM
Measure the cam follower bores in the cylinder head with a telescope gage and micrometer and record the
readings. Measure the diameter of the cam followers with a micrometer. Record the readings and compare
the readings of the followers and bores to determine the cam follower-to-bore clearances (refer to
Specifications).
Inspect the push rods and spring seats for wear.
Examine the cam follower springs for wear or damage and check the spring load.
The current push rod spring (Fig. 6) is made from 0.1920-inch diameter wire and was first used only in the
injector cam follower position, effective with engine 4D-5323.
Effective with engine 4D-8549, the new spring is also used in the exhaust valve cam follower position. The
former push rod spring was made from 0.1770-inch diameter wire.
Use spring tester J 22738-02 to check the spring load (Fig. 5). Replace the current-type spring when a load of
less than 250 pounds (1112 N) will compress it to a length of 2.1406 inches. Replace the former-type spring
when a load of less than 172 pounds (765 N) will compress it to a length of 2.1250 inches.
It is recommended that if one former type push rod spring requires replacement, all of the former-type springs
in either the injector or valve cam follower positions be replaced by the current-type spring. A new design
upper spring seat is required with the use of the current push rod spring.
Figure 6. Spring Identification
Figure 5. Testing Cam Follower
Spring
85
