Adjusting Intake and Exhaust Valve Clearance

d. Compression V a r i a t i o n . After all 12

cylinders are checked, determine the pressure

difference between high and low cylinder

readings. This variation should not exceed 70

psi.

e. Engine Motoring RPM. If compression

d a t a e x c e e d s t h e a b o v e specifications. the

engine motoring rpm should be checked to be

sure that it is 140 to 180 rpm. Compression

should be checked again to confirm the previous

readings before submitting an engine for

overhaul.

4-23. Adjusting Intake and Exhaust

V a l v e Clearance

When checking and / or adjusting valve

c l e a r a n c e , i t is necessary to first remov e t h e

cooling fan vanes, fans, fan shroud, top covers,

and oil coolers to gain access to valve adjusting

screw cover plates. R e f e r to Table 4-9 for in-

structions pertinent to the removal of the above

items, and the procedures involved in the ad-

j u s t m e n t o f t h e i n t a k e and e x h a u s t v a l v e

clearances.

1. Install gage assembly -4910-870-6283 (A) on adapter

- 4910-795-7961 and tighten securely.

2. Crank engine using starter motor and check cylinder

compression. It must be within 330 to 480 psi at engine

cranking speed.

3. Depress gage vent valve (B) to release pressure and

reset gage to zero after compression reading is taken.

Recheck reading. Test compression on all cylinders in

the same manner.

Figure 4-185. Checking cylinder compres-

sion using gage assembly-4910-870-6283

and compression adapter-4910-795-7961.

4-95