DETROIT DIESEL
Engine Tune-Up
FOUR VALVE CYLINDER HEADS
Cold Engine
1. Place the speed control lever in the idle speed
position. If a stop lever is provided, secure it in the no-fuel
position.
2. Remove the loose dirt from the valve rocker cover(s)
and remove the cover(s).
3. Rotate the crankshaft until the injector follower is fully
depressed on the cylinder to be adjusted.
CAUTION: If a wrench is used on the crankshaft bolt,
do not turn the engine in a left-hand direction of
rotation as the bolt will be loosened.
4. Loosen the exhaust valve rocker arm push rod locknut.
5. Place a .027" feeler gage, J 9708, between the end of
one valve stem and the rocker arm bridge (Fig. 2). Adjust
the push rod to obtain a smooth pull on the feeler gage.
Fig. 2 - Adjusting Valve Clearance (Four-Valve
Cylinder Head)
6. Remove the feeler gage. Hold the push rod with a
5/16"wrench and tighten the lock -nut with a1/2 " wrench.
7. Recheck the clearance. At this time, if the adjustment is correct, the .025" gage will pass freely between the end of
one valve stem and the rocker arm bridge and the .027" gage will not pass through. Readjust the push rod if necessary.
8. Check and adjust the remaining exhaust valves, in the same manner as above.
Hot Engine
Maintaining normal engine operating temperature is particularly important when making the final valve clearance
adjustment. If the engine is allowed to cool off before setting any of the valves, the clearance, when running at full load,
may become insufficient.
1. With the engine at normal operating temperature (160-185F or 71-85C), recheck the exhaust valve clearance with
gage J 9708. At this time, if the valve clearance is correct, the .023" gage should pass freely between the end of one
valve stem and the rocker arm bridge and the .025" feeler gage should not. Readjust the push rod, if necessary.
2.
After the exhaust valve clearance has been adjusted, check the fuel injector timing.
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