3-35. CYLINDER HEAD AND VALVE REPAIR (Contd)
d. Assembly and Testing (Contd)
30. Cylinder head
c. Turn hand shutoff valve to
assembly (1) (Contd)
open position and hold down
push button to operate valve
vacuum tester (58).
d. Operate vacuum tester (58)
Close hand shutoff valve and
until vacuum gauge indicates
release push button to stop
between 18 and 25 in. of
e. Record vacuum drop to
1. Start timing as soon as gauge
determine satisfactory valve
hand reaches 18 in. of vacuum.
2. Stop timing when gauge hand
reaches 8 in. of vacuum.
3. If time is less than 10 seconds,
valve seating is unsatisfactory.
Perform step 30f if valve seating
f. Tap stem end of valve (13) or
Lapping valves is permissible, if
(14) with soft-nose mallet and
necessary, to create an air-tight
repeat vacuum test.
g. Check for leaking connections
Clean if necessary.
in valve vacuum tester (58).
h. Check for leaks between valve
1. Apply a coat of grease to out-
insert (12) or (15) and valve insert
side diameter of insert to make a
center bore in cylinder head (9).
greade seal between insert and
2. Vacuum test (refer to step 30d)
and inspect grease seal.
3. If there is a break in grease seal,
remove valve (13) or (14). Stake
valve seat with valve seat insert
staking tool (36) and driver (37).
Two adjusting screws (30)
Install on exhaust valve
and nuts (29)
Two adjusting screws (20)
Install on intake valve
and nuts (21)
Two exhaust valve
Install on valve crosshead
crossheads (28) and
guides (8) on cylinder head (9).
intake valve crossheads (22)
Step 34 is for M915/Big Cam I vehicles only.
Install all cylinder head pipe plugs
and tighten to specifications shown
PIPE PLUG SIZE
FOLLOW-ON TASK: Install cylinder head assembly (para. 3-71).