Figure 4-41. Valve Arrangement

Note

Before adjusting the valve clearance, run

the engine at approximately 1200 RPM, for

a minimum of 30 minutes in order to

temperatures.

Then

stabilize

engine

proceed as follows:

a. Reduce the engine speed to approx-

imately 650 RPM, then shut engine off.

Apply parking brake.

b. Remove the rocker arm cover hold down nuts.

Figure 4-41. Valve Arrangement

c. Jar the rocker arm cover with the heel of your

hand or a soft leather hammer to loosen the gasket

from the cylinder head.

d. Remove the rocker arm cover.

e. "Bump" the starter and crank the engine until

the No. 4 (farthest from fan end) exhaust valve is

fully up and intake valve is just starting its

downward stroke, At this point the No. 1 valves

should both be up. See figure 4-41.

f. Loosen the lock nut and the adjusting screw on

the rocker arm stud and with a flat feeler gauge

adjust the intake valve clearance to have 0.010

inch. Adjust the exhaust valve to have 0.020 inch

clearance - engine hot (normal water jacket

Figure 4-42. Setting Valve Lash

temperature). See figure 4-42.

g. Now tighten the lock nut and continue with

4 - 3 9 . VALVE

CLEARANCE

(LASH)

the other valves by cranking the engine until No. 3

ADJUSTMENT. Maintaining the proper valve lash

exhaust valve is up and intake valve is just starting

setting is one of the most important factors

down. Now check and adjust No. 2 cylinder valve

relating to excellent engine performance and long

clearance as outlined in steps e, f and g above.

life. Valve lash that is adjusted too tight causes the

valves to operate too early and close too late. This

h. Crank engine until No. 1 exhaust valve is fully

does not allow the valve to remain on the seat long

up and intake valve is just starting down. Check

enough to cool properly and results in early valve

and adjust No. 4 cylinder valve clearance.

warping and burning. When the valves are allowed

to operate with too loose a setting, they open too

i. Finally, crank engine until No. 2 exhaust valve

late and close too early. When this condition exists,

is fully up and intake valve is just starting down.

the ramp on the camshaft lobe, which slows down

Check and adjust valve clearance for No. 3

the closing of the valve before it contacts the seat,

cylinder.

is not allowed to perform its function. Therefore,

the valve strikes the seat while traveling at a very

j. After all adjustments are made, clean the

high speed, resulting in increased valve and

gasket surfaces, install a new valve cover gasket,

camshaft wear and possible breakage of the valve

and replace the valve cover.

due to the high impact force.

4-31