Assembly Of Engine; Prior To Assembly; Crankshaft And Main Bearing Installation - GMC 1990 Light Truck Repair Manual

6A1-22 2.5 LITER L4 ENGINE
• Mount the crankshaft in V-blocks or between
centers.
• Use a dial indicator as shown.
• If the main bearing journals are misaligned,
the crankshaft is bent and must be replaced
along with the main bearings.

PRIOR TO ASSEMBLY

The importance of cleanliness during the assembly
procedure cannot be overstressed. Dirt will cause
premature wear of the rebuilt engine.
Lubricate all moving parts lightly with engine oil or
engine assembly lubricant (unless specified otherwise)
during assembly. This will provide initial lubrication when
the engine is started.
CRANKSHAFT AND MAIN
BEARING INSTALLATION
Service bearing inserts are available in standard size
and 0.001-inch undersize.
+4-
Install or Connect (Figures 5 and 39)
1. Upper main bearing inserts (86 and 72) to the block.
• If any previously used or undersized bearings
are used, make absolutely certain that they
are fitted to the proper journal.
2. Crankshaft (88). Take care not to damage the thrust
areas.
3. Lower bearing inserts (86 and 72) to the bearing
caps.
Measure
Main bearing clearance. Refer to GENERAL
ENGINE MECHANICAL (SEC. 6A) in this
manual.
3. Engine oil to the lower main bearing inserts.

ASSEMBLY OF ENGINE

Figure 38—Checking Crankshaft Runout
4. Main bearing caps (except the rear cap) with the
selected lower main bering inserts (86 and 72). Be
sure to put the main bearing cap in their original
positions, with the arrows facing the front of the
engine.
5. Bolts (125). Make sure the special bolt, which
retains the oil pump pickup tube and screen is
installed in the proper position. (#4 main bearing
cap, camshaft side hole.)
Tighten
• Main bearing cap bolts to 88 N-m (65 ft. lbs.).
6. Rear main bearing cap to the block.
7. Rear main bearing cap bolts. Tighten the bolts
temporarily to 14 N m (10 ft. lbs.).
tH Measure (Figure 40)
Crankshaft end play, as follows:
Tap the end of the crankshaft first rearward
then forward with a lead hammer. This will line
up the rear main bearing and crankshaft thrust
surfaces.
Tighten the rear main bearing cap bolts to 88
N-m (65 ft. lbs.).
With the crankshaft forced forward, measure
at the front end of the rear main bearing with a
feeler gage. The proper clearance is 0.09 -
0.20 mm (0.0035 - 0.0085-inch).
Crankshaft for binding. Try turning the crankshaft to
check for binding. If the crankshaft does not turn
freely, loosen the main bearing cap bolts, one pair at
a time, until the tight bearing is located. Burrs on the
B-02792