GMC 4000 Series Service Manual page 279

Sec. 6A
Page 268
GASOLINE ENGINES
Figure 19— Valve Adjustment on In-Line Engine
8. Connect choke cable and adjust as directed
in ENGINE FUEL SYSTEM (SEC. 6M) of this manual.
9. Connect throttle rods at bellcrank and in­
stall throttle return spring.
10. Install air cleaner, start engine, check for
leaks and adjust carburetor idle speed and mixture.
ROCKER ARM COVER
REPLACEMENT
REMOVAL
1. Disconnect crankcase ventilation hose at
rocker arm cover.
2. Remove air cleaner.
3. Disconnect temperature wire from rocker
arm cover clips.
4. Remove cover attaching screw s, then re­
move cover.
CAUTION: DO NOT pry rocker arm
cover loose. Gaskets adhering to cylinder
head and rocker arm cover may be loos­
ened by bumping end of rocker arm cover
rearward with palm of hand, or a rubber
mallet.
INSTALLATION
1. Clean gasket surfaces on cylinder head and
rocker arm cover with degreaser, then using a
new gasket, install rocker arm cover and torque
screw s to specifications.
2. Connect temperature wire at rocker arm
cover clips.
3. Install air cleaner.
4. Connect crankcase ventilation hose.
G M C S E R V I C E M A N U A L
VALVE MECHANISM REPLACEMENT
REMOVAL
directed.
rocker arms and push rods.
and push rods in a rack so they may be reinstalled
in the same location.
INSTALLATION AND ADJUSTMENT
rocker arm balls are being installed, coat bearing
surfaces of rocker arms and rocker arm balls
with Molykote or its equivalent.
■ 3563
in lifter socket.
rocker arm nuts. Tighten rocker arm nuts until
all lash is eliminated.
of camshaft lobe as follows:
each cylinder position (plug wire), then disconnect
plug wires at spark plugs and coil and remove dis­
tributor cap and plug wire assembly (if not p re­
viously done).
to No. 1 cylinder position and breaker points are
open. Both valves on No. 1 cylinder may now be
adjusted.
the push rod, then turn in adjusting nut until all
lash is removed. This can be determinedby check­
ing push rod side play while turning adjusting nut
(fig. 19). When play has been removed, turn ad­
justing nut one full additional turn (to center the
lifter plunger).
at a time, in the same manner.
assembly.
structed.
as directed in ENGINE FUEL SYSTEM (SEC. 6M)
of this manual.
tion. The lifters are sim ple in design, readjust­
ments are not necessary, and servicing of the lift­
ers requires only that care and cleanliness be
exercised in the handling of parts.
LOCATING NOISY LIFTERS
1. Remove rocker arm cover as previously
2. Remove rocker arm nuts, rocker arm balls,
NOTE: Place rocker arm s, rocker arm balls
NOTE: Whenever new rocker arms and/or
1. Install push rods. Be sure push rods seat
2. Install rocker arm s, rocker arm balls and
3. Adjust valves when lifter is on base circle
a. Mark distributor housing, with chalk, at
b. Crank engine until distributor rotor points
c. Back out adjusting nut until lash is felt at
d. Adjust the remaining valves, one cylinder
4. Install distributor cap and sparkplug wire
5. Install rocker arm cover as previously in­
6. Adjust carburetor idle speed and mixture
VALVE LIFTERS
Hydraulic valve lifters seldom require atten­
Locate a noisy valve lifter by using a piece of