GMC 1989 Light Duty Truck Repair Manual page 411

• Crankshaft run-out.
• Mount the crankshaft in V-blocks or between
centers.
• Use a dial indicator.
• If the main journals are misaligned more than
0.025 mm, the crankshaft is bent and must be
replaced, along with the main bearing.
PRIOR TO ASSEMBLY
The importance of cleanliness during the assembly
p ro ced ure cannot be o verstressed. D irt w ill 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
Main bearings are of the precision insert type and do
not use shims for adjustment. If clearances are excessive,
a new bearing plus both upper and lower inserts will be
required. Service main bearings are available in standard
size, 0.016, and 0.032 mm undersize. Service rod bearings
are available in standard size and 0.026 mm undersize.
Selective fitting of both rod and main bearing inserts is
necessary in production to obtain close tolerances. For
this reason you may find one half of a standard insert with
one half of a 0.032 mm undersize insert which will
decrease the clearance 0.016 mm from using a full
standard bearing.
■n- Install or C onnect
1. Upper main bearing inserts to the block.
Im portant
• If any undersized bearings are used, make
sure they are fitted to the proper journals.
2. Crankshaft.
3. Lower main bearing inserts to the main bearing
caps.
ASSEMBLY OF ENGINE
2.8 LITER V-6 6A2-19
Figure 28— Measuring the Crankshaft Journals
A. Anaerobic Sealant (GM Part
No. 1052756 or Equivalent)
B. RTV Sealant (GM Part No. 1052942
or Equivalent)
Figure 29— Applying Sealer to Rear Main Bearing Cap
M easure
• Main bearing clearance. Refer to GENERAL
ENGINE MECHANICAL (SEC. 6A).
Apply engine oil to the main bearing inserts.
4.
New O-ring (if used) into the rear main bearing cap.
5. Thin coat of a na erob ic sealant (GM Part No.
1052756 or equivalent) to the rear main bearing cap
(figure 29).
• Do not allow sealer on the crankshaft or the
seal.
6
A sm all am ount of RTV sealant (GM Part No.
.
1052942 or equivalent) to the rear 4 mm of the rear
bearing cap sealing surface (figure 29).
• Do not allow sealer on the crankshaft or the
seal.
F-05901