TM 5-3895-346-14
EXHAUST-VALVE CLEARANCE ADJUSTMENT
ENGINE OVERHAUL
EXHAUST-VALVE CLEARANCE ADJUSTMENT
The correct exhaust-valve clearance at normal engine operating temperature is important for smooth, efficient
operation of the engine.
Insufficient valve clearance can result in loss of compression, misfiring cylinders, and eventually burned valve
seats and valve seat inserts. Excessive valve clearance will result in noisy operation, increased valve face
wear, and valve lock damage.
Whenever the cylinder head is overhauled, the exhaust valves are reconditioned or replaced, or the valve
operating mechanism is replaced or disturbed in any way, the valve clearance must first be adjusted to the cold
setting to allow for normal expansion of the engine parts during the engine warm-up period. This will ensure a
valve setting that is close enough to the specified clearance to prevent damage to the valves when the engine
is started.
All of the exhaust valves may be adjusted in firing order sequence during one full revolution of the crankshaft.
Refer to the General specifications at the front of the manual for the engine firing order.
Valve Clearance Adjustment (Cold Engine)
1.
Remove the loose dirt from the valve rocker cover and remove the cover.
2.
Place the governor speed control lever in the idle speed position. If a stop lever is provided, secure
it in the stop position.
3.
Rotate the crankshaft, manually or with the starting motor, until the injector follower is fully
depressed on the particular cylinder to be adjusted.
CAUTION
If a wrench is used on the crankshaft bolt at the front of the engine, do not turn the
crankshaft in the left-hand direction of rotation or the bolt may be loosened.
4.
Loosen the exhaust valve, rocker arm, push
rod locknut.
5.
Place a 0.027-inch feeler gage, J 9708-01,
between the end of one exhaust valve stem and the
rocker arm bridge (Fig. 1). Adjust the push rod to obtain
a smooth pull on the feeler gage.
6.
Remove the feeler gage. Hold the push rod
with a 5/16-inch wrench and tighten the locknut with a
1/2-inch wrench.
7.
Recheck the clearance. At this time, if the
adjustment is correct, the 0.025-inch gage will pass
freely
Figure 1. Adjusting Valve Clearance (Four-
Valve Head)
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