GMC 4000 Series Service Manual page 292

1 Shaft and Inner
Rotor Assembly
2 Pump Outlet
3 Pump Body
4 Governor Spinner
Shaft
5 Governor Spinner
Valve
Governor Spinner
6
Cover
7 Governor Pressure
Outlet
Figure 4 3 — Engine Oil Pum p with Hydraulic Governor
3. To change engine rpm, hold weight with
screwdriver while turning nut (10, fig. 43). Tight­
ening nut 1/8 turn increases engine speed approx­
imately 100 rpm. Loosening nut 1/8 turn lowers
engine governed speed approximately 100 rpm.
4. After adjusting the governor, install oil pan
with enough screws to hold pan in place while re­
checking governed speed. Be sure to add engine
oil to mark on dipstick. With oil warmed up, re­
check no-load speed.
5. When governor performance is satisfac­
tory, install balance of oil pan screws and tighten
evenly and firm ly.
HYDRAULIC GOVERNOR
TROUBLESHOOTING
With engine warmed up to 180°F., installpres-
sure gauge and tee in governor line at carburetor.
G M C S E R V I C E M A N U A L
8
Shaft Thrust Washer
9 Valve Spring
10 Valve Adjusting Nut
11 Rotor Cover and
Spinner Housing
12 Drive Coupling
13 Outer Rotor
14 Inner Rotor
15
Oil Pump Pressure
R elief Valve Spring
Cap
TP M -7 78 7 -1
Figure 4 4 — Timing M arks on V6 Engine (Typical)
Run engine at full throttle (no-load) momentarily
and check engine speed on tachometer and note
p ressure on gauge in line. Properly functioning
governor will provide 3400 rpm with 8-10 psi on
gauge (351M engine). Procedure for adjusting gov­
ernor spinner is given previously.
CHECKING ENGINE VALVE TIMING
When a check of valve timing is necessary,
the following procedure may be used referring to
markings at crankshaft pulley hub or pulley for
determining upper-dead-center on No. 1 cylinder:
1. Remove left-hand rocker cover from cyl­
inder head to provide access to rocker arms at
No. 1 cylinder.
2. Turn engine clockwise (viewed from front
of engine) to UDC #1 mark at crankshaft pulley (fig.
44) on compression stroke. Both the intake and the
exhaust valve on No. 1 cylinder will then be closed.
3. On all V6 engines adjust clearance to exact­
ly 0.099 inch at No. 1 exhaust valve (front valve).
4. Turn engine clockwise until No. 1 exhaust
valve opens and begins to close, then with fingers,
try turning push rod of No. 1 exhaust valve as
engine is cranked slowly. When push rod rotates
with finger pressure, the 5-degree (BUDC) mark
on pulley should be at pointer. This will be about
one revolution from starting point. If push rod
can be rotated at any point between 10 degree mark
and UDC #1 mark, the valve timing is correct. Be
sure to adjust exhaust valve clearance to 0.018 inch
after performing the foregoing check.
NOTE: When making check of valve timing, if
timing chain is improperly installed, there will be
15-degree out-of-time condition for each m is­
matched tooth on sprocket.
Sec. 6A
Page 281
GASOLINE ENGINES