TM 5-3895-382-24
Not enough valve lash can be the cause of rapid wear of the
camshaft and valve lifters. Not enough valve lash can indicate
that the seats for the valves are defective.
Valves become defective due to the following causes:
Fuel injector nozzles that operate incorrectly.
Excessive dirt and oil are present on the filter for the
inlet air.
Incorrect fuel settings on the fuel injection pump.
The load capacity of the engine Is frequently exceeded.
Too much valve lash can cause broken valve stems, springs,
and spring retainers. Too much valve lash can be an
indication of the following problems:
worn camshaft and valve lifter
worn rocker arms
bent pushrods
broken socket on the upper end of a pushrod
loose adjustment screw for the valve lash
If the camshaft and valve lifters show rapid wear, look for fuel
in the lubrication oil or dirty lubrication oil as a possible cause.
The valve lash is measured between the top of the valve stem
and the rocker arm lever.
NOTE:
Number 1 cylinder is at the front of the engine.
Illustration 64
Setting The Valve Lash.
(1) Adjustment screw
(2) Feeler gauge
Perform the following procedure in order to adjust the valve
lash:
1.
Set the top center position for number 1 piston on the
compression stroke. Before adjustments are made,
lightly tap each rocker arm at the top of the adjustment
screw. Use a soft mallet to ensure that the lifter seats
against the camshaft's base circle.
2.
Measure the valve lash for the inlet and exhaust valves
on cylinder 1. If necessary, make an adjustment to the
valve lash on the inlet and the exhaust valves for
number 1 cylinder.
a.
Loosen the valve adjustment locknut that is on the
adjustment screw (1).
b.
Place the appropriate feeler gauge (2) between the
rocker arm and the valve. Turn the adjustment screw
(1) while the valve adjustment locknut is being held
from turning. Adjust the valve lash until the correct
specification is achieved.
c.
After each adjustment, tighten the valve adjustment
locknut while the valve adjustment screw (1) is being
held from turning.
3.
Turn the crankshaft for 180 degrees in the direction of
the normal engine rotation. Measure the valve lash of
the inlet valve and the exhaust valve of number 3
cylinder. If necessary, make an adjustment to the inlet
valve and the exhaust valve on number 3 cylinder.
a.
Loosen the valve adjustment locknut that is on the
adjustment screw (1).
b.
Place the appropriate feeler gauge (2) between the
rocker arm and the valve. Turn the adjustment screw
(1) while the valve adjustment locknut is being held
from turning. Adjust the valve lash until the correct
specification is achieved.
c.
After each adjustment, tighten the valve adjustment
locknut while the valve adjustment screw (1) is being
held from turning.
4.
Turn the crankshaft for 180 degrees in the direction of
the normal engine rotation. Measure the valve lash of
the inlet valve and the exhaust valve of number 4
cylinder. If necessary, make an adjustment of the valve
lash on number 4 cylinder.
a.
Loosen the valve adjustment locknut that is on the
adjustment screw (1).
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