GMC 1989 Light Duty Truck, Repair Manual, Page: 505 / 998

V8 ENGINE 6A5-15
Figure 26— Checking the Block Gasket Surface
Figure 27— Main Bearing Cap Shim Location (Typical)
— Cylinder walls.
— Coolant jackets.
— Main bearing webs.
— Engine mount bosses.
4. Main bearing bores and main bearing caps.
— All main bearing bores should be round and
uniform in ID at all bearing supports.
— The area w here the main bearing inserts
contact the main bearing bore should be
smooth.
— If a main bearing cap is damaged and requires
replacement, replace it as outlined later.
M easure (Figure 26)
Head gasket surface distortion . Use a straig ht
edge and feeler gage to ch eck for flatness of the
m illed surface at the top of the cylind er block.
T h e s u rfa c e m u s t be fla t ( w ith in 0 .1 0 m m
[0 .0 0 4 -in c h ]) to a s s u re p ro p e r h e a d g a s k e t
sealing.
MAIN BEARING CAP REPLACEMENT
0
Install or C onnect
1. New m ain bearing cap. The arrow on the main
b e a rin g ca p fa c e s th e fro n t o f th e e n g in e
(opposite the flyw heel).
2. M ain bearing cap bolts.
Tighten
Bolts to “ S p e c ific a tio n s .”
M easure (Figure 27)
• M ain bearing vertical ID (inside diam eter).
Use an inside m icrom eter.
• This d im ension should be the sam e as the
other m ain bearing bore vertical diam eters.
• If it is necessary to increase the vertical ID,
use an equal th ickn e ss of special service
bearing cap shim s at each side of the cap to
provide th e sam e d im en sion as at the other
bores. T h is is n e c e s s a ry to a s s u re th e
p roper crush on the bearing inserts w hen
the e ngine is assem bled.
CYLINDER BORES
Inspect
L1
C ylin de r bores for sco ring and other dam age.
M easure
C y lin d e r o u t o f ro u n d a n d ta p e r. R e fe r to
G E N E R A L EN G IN E M E C H A N IC A L (SEC. 6A).
Cylinder Bore Reconditioning
• Refer to GENERAL ENGINE MECHANICAL (SEC.
6A).
PISTON AND CONNECTING ROD
ASSEMBLIES
Refer to GENERAL ENGINE MECHANICAL (SEC. 6A)
and perform the following:
❖
i g i
13
*
D isassem ble
C om ponents as required.
Clean
C om ponents as outline d.
Inspect
C om ponents as outline d.
M easure
• Piston pin diam eter and pin to piston clearance.
• P iston to bore c le a ra n c e , and fit p is to n s as
outlined.
Assem ble
C om ponents as outlined.