Checking Valve T Im In; W Ater Pump In S Ta Lla Tio; Therm Ostat Housing In S Ta Lla Tio - Chevrolet 1988 Light Duty Truck Repair Manual

6A4-30 4.8 LITER L6
Figure 60—Adjusting the Valves
CHECKING VALVE TIMING
Tool Required:
J-8520 Dial Indicator Adaptor
W hen it becomes necessary to make a check of valve
tim ing, the procedure following may be used:
1. Loosen the nut at the #1 intake valve rocker arm,
swing the rocker arm away from the pushrod, then
remove the pushrod.
2. Install a dial indicator, along with J-8520 (figure 61).
Turn the crankshaft until the #2 exhaust valve opens
and the tim ing mark on the vibration dam per is
aligned with the " 0 " mark on the tim ing marker.
3. P o s itio n th e d ia l in d ic a to r to m e a s u re lifte r
m ovem ent and set in d ica to r at zero. Turn the
crankshaft 360 degrees and read the indicator. On
c o rre c tly tim e e n g in e s th e in d ic a to r w ill read
0.012-0.020-inch.
4. If the reading is not as shown, reset the indicator at
zero and turn the crankshaft 360 degrees, then read
the in d ic a to r a g a in . If re a d in g is now w ith in
specifications, the engine is tim ed properly.
Figure 61— Measuring Camshaft Lobe Lift
5. The following chart shows indicator readings with
gears properly indexed for 4.8L engines and the
indicator readings resulting from im properly indexed
gears.
Engine
Camshaft Part Number
Valve Lift
Dial
Indicator
Readings
ROCKER ARM COVER AND
B-07858
INSTALLATION
Install or Connect (Figures 4 and 5)
1. Gasket (8).
2. Rocker arm cover (7).
3. Bolts (3), clips (2) and reinforcem ents (4).
Q
Tighten
• Bolts (3) to 4.3 N m (38 in. lbs.).
4. Gaskets (114).
5. Pushrod covers (179).
6. Bolts (178).
Tighten
• Bolts (178) to 9.0 N m (80 in. lbs.).
WATER PUMP INSTALLATION
Install or Connect (Figure 5)
1. Gasket (169).
2. Water pum p (171).
3. Bolts (170).
Tighten
• Bolts (170) to 20 N m (15 ft. lbs.).
THERMOSTAT HOUSING
-►+ Install or Connect (Figure 4)
1. Gasket (49).
2. Therm ostat housing (50).
3. Bolts (51).
Tighten
B-03714
• Bolts (51) to 38 N m (28 ft. lbs.).
4. Hose (47).
Gears Properly Indexed
One Tooth Advanced
One Tooth Retarded
PUSHROD COVER
INSTALLATION
INSTALLATION
4.8L
3848000
0.405"
0.016" ± 0.004"
0.0379"
0.0068"