GMC 4000 Series Service Manual page 291

Sec. 6A
Page 280
GASOLINE ENGINES
1 Drive Housing
2 Housing Nut
3 Tachometer Adapter
Figure 41 — Tachometer Drive Assem bly
INSTALLATION
1. Place new pump-to-block gasket on oil
pump flange, and insert pump drive shaft in drive
socket in pump shaft.
2. Set oil pump assembly in position at cylin­
der block and turn pump as necessary to engage
the pump drive shaft with drive socket at upper
end.
3. On engines (351M) with hydraulic type gov­
ernor, position oil line (2, fig. 40) at fittings on
cylinder block and oil pump and start oil line nuts.
4. Install oil pump-to-cylinder block bolts and
tighten to 30 to 35 foot-pounds torque. Tighten oil
line nuts on engine with hydraulic governor.
5. Install engine oil pan, following instructions
previously given in "Oil Pan Replacement."
2 Housing
3 Gear and Shaft Assy.
4 Thrust Washer
5 Cover and Bushing Assy.
Figure 4 2 — Tachometer M ech a n ical Drive Com ponents
G M C S E R V I C E M A N U A L
4 Gasket
5 Adapter Mounting Bolt
Flywheel Housing t-4 3 8 9
6
6 Cover Screw and Lock
Washer
7 Drive Gear
8 Drive Bolt (In Camshaft)
9 Gasket
10 Bushing (In Housing)
11 Gear Shaft Bushing
TACHOMETER DRIVE ADAPTER
REPLACEMENT
REMOVAL (Fig. 41)
1. Remove floor pan from cab on conventional
cab models, or remove shield from cab rear sup­
port on tilt cab models.
2. Disconnect tachometer drive shaft housing
(1) from adapter (3).
3. Remove two bolts and lock washers (4) at­
taching adapter (3) to cylinder block.
4. Remove adapter assembly and gasket from
cylinder block.
NOTE: If there is insufficient clearance for
adapter removal, try turning engine crankshaft to
position drive bolt (8, fig. 42) in camshaft so drive
slot is in vertical position. In some cases it may
be necessary to use small pencil type grinder to
remove necessary amount of stock from flywheel
housing to permit disengagement of tongue on gear
shaft from drive slot in bolt (8, fig. 42).
5. Referring to figure 42, remove cover (5)
and inspect teeth on gears (3 and7 ).Clean oil holes
in cover.
INSTALLATION
1. Lubricate adapter parts with clean engine
oil and attach cover to housing with screw s and
lock washers (6, fig. 42).
2. Check drive bolt (8, fig. 42) to make sure it
is firm ly tightened into threads in camshaft. If
necessary, turn engine crankshaft to position drive
bolt slot in vertical position.
3. Align tongue on adapter shaft with drive
bolt slot, then place new gasket at cylinder block
and install adapter assembly. Connect flexible
drive shaft housing to adapter (fig. 41).
4. Check tachometer drive cable and housing
routing. There must be no sharp bends or kinks
in the assem bly. Lubricate tachometer drive cable
with correct lubricant (Type ST-640) or equivalent.
GOVERNOR SPINNER VALVE
ADJUSTMENT
If governed speed on engines equipped with
hydraulic type governor is not as specified in ap­
plicable "Gasoline V6 Engine Tune-up Chart" the
speed can be changed by adjusting spinner valve
spring tension.
To change the engine governed speed proceed
as follows:
1. Drain oil from oil pan and remove oil pan
from engine.
2. Turn engine crankshaft as necessary to
position the spinner valve weight and adjusting nut
so wrench and screwdriver can be used to make
adjustment.