VALVE OPERATING MECHANISM
It is also possible to replace a push rod, push rod spring, the spring seats, or a cam follower without removing
the cylinder head. However, these parts are more easily changed from the lower side when the cylinder head is
off the engine. Both methods are covered in this section.
To replace the exhaust valves and valve seat inserts, the cylinder head must be removed (refer to Cylinder
Remove Rocker Arms and Shaft
Clean and remove the valve rocker cover.
Remove the fuel pipes from the injector and the fuel connectors.
Immediately after removing the fuel pipes, cover the injector fuel inlet and outlet
openings with shipping caps to prevent dirt or foreign material from entering.
Turn the crankshaft, or crank the engine with the starting motor, to bring the injector and valve
rocker arms in line horizontally.
Do not bar the crankshaft in a left-hand direction of rotation with a wrench or
barring tool on the crankshaft bolt, or the bolt may be loosened.
Remove the two bolts which secure the rocker arm shaft brackets to the cylinder head. Remove
the brackets and shaft.
When removing the rocker arm shaft, fold the three rocker arms back just far
enough so the shaft can be removed. Do not force the rocker arms all the way
back with the shaft in place as this may impost a load that could bend the push
Loosen the locknuts at the upper ends of the push rods, next to the clevises, and unscrew the
rocker arms from the push rods.
If the rocker arms and shafts from two or more cylinders are to be removed, tag
them so they may be reinstalled in their original positions.
Wash the rocker arms, shaft, brackets, and bolts with clean fuel oil. Use a small wire to clean out the drilled oil
passages in the rocker arms and rocker shaft bolts. Dry the parts with compressed air.
Inspect the rocker arm shaft, injector rocker arm bushings, or valve rocker arm bores for wear. A maximum
shaft to bushing (or bore) clearance of 0.004 inch is allowable with used parts (refer to Specifications). Service
replacement injector rocker arm bushings must be reamed to size after installation.
Inspect the rocker arms for galling or wear on the pallets (valve or injector contact surfaces). If worn, the
surface may be refaced up to a maximum of 0.010 inch. However, proceed with caution when surface grinding
to avoid overheating the rocker arm. Maintain the radius and finish as close to the original surface as possible.
Also, inspect the valve bridges (four-valve head) for wear.