Chevrolet 1991 Light Duty Truck Repair Manual page 477

(5.0 and 5.7L Engines)
PRIOR TO ASSEMBLY
The importance of cleanliness during the assembly
procedure cannot be overstressed. Dirt will cause pre­
mature 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 exces­
sive, a new bearing will be required. Service bearings
are available in standard size and 0.001-inch,
0.002-inch, 0.010-inch, and 0.020-inch undersize. 0.009
inch is available for 5.0L and 5.7L engines only.
Selective fitting of both rod and main bearing inserts
is necessary to obtain close tolerances. For this reason
you may use, for example, one half of a 0. 001-inch
undersize insert which will decrease the clearance
0.0005-inch from using a full standard bearing.
UNDERSIZE MAIN JOURNALS (5.0L AND 5.7L
ENGINES)
• On 5.0L and 5.7L engines, when a production
crankshaft cannot be precision fit by the method
described previously, it is then ground 0.009-inch
undersize ON ONLY THOSE MAIN JOURNALS
THAT CANNOT BE PROPERLY FITTED. ALL
JOURNALS WILL NOT BE NECESSARILY BE
GROUND. A 0.009-inch undersize bearing or
0.010-inch undersize bearing will then be used for
REAR CRANKSHAFT
OIL SEAL RETAINER
(5.0L AND 5.7L ENGINES)
Disassemble (Figure 51)
• Rear crankshaft oil seal. Insert a screwdriver into
the notches provided in the seal retainer and pry
the seal out (figure 51).
; u u
Clean
■ i
• All traces of old gasket from the retainer.
( y | Inspect
• Retainer for cracks, porosity, and damage to the
sealing surfaces.
m Important
• Install the new rear crankshaft oil seal with the
proper tool, after the retainer is assembled to the
engine, as outlined later.
ASSEMBLY
precision fitting in the same manner as previously
described.
OVERSIZE REAR MAIN BEARING THRUST FACES
(5.0L AND 5.7L ENGINES)
• Some 5.0L and 5.7L production engines may have
rear main bearings that are 0.008-inch wider than
standard across the thrust faces.
• The crankshaft on these engines can be identified
by " .008"stamped on the rear counterweight.
• If the rear main bearings are replaced, they must
have the proper distance between thrust faces to
obtain correct crankshaft end play.
0
Install or Connect (Figures
1. Upper main bearing inserts to the block.
ELI
Important
• 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.
Measure
• Main bearing clearance. Refer to GENERAL
ENGINE MECHANICAL (SEC. 6A).
• Apply engine oil to the main bearing inserts.
4. Main bearing caps (except rear cap) and bolts to
the block.
V8 ENGINES 6A5-25
52, 53, and 54)
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