Main Bearing Removal (Without Removing Crankshaft); Cleaning, Inspection, And Repair; Block; Piston And Connecting Rod A Ssem Bly - GMC 1990 Light Truck Repair Manual

6A3-10 4.3 LITER V-6
MAIN BEARING REMOVAL
(WITHOUT REMOVING
CRANKSHAFT)
R e m o ve o r D is c o n n e c t
Tool Required:
J 8080, Main Bearing Remover/Installer
1. Main bearing caps.
• Check the main bearing caps for location
markings. Mark the caps if necessary. The
caps must be returned to their original
locations during assembly.
2. Lower main bearing inserts from the main bearing
caps.
3. Upper main bearing inserts.
• Insert J 8080 into the crankshaft oil hole
(figure 13).
• Rotate the crankshaft to turn the bearing insert
out of the block.

CLEANING, INSPECTION, AND REPAIR

A solvent tank, large enough to hold the larger engine
parts, will be needed along with various bristle brushes
and a gasket scraper. A source of compressed air will be
helpful in the cleaning operations.
Precision measuring tools will be required for the in­
spection procedure. These include: micrometers, cylinder
bore gage, feeler gages, dial indicator set, etc. The in­
spection work, performed with the proper method and
tools, is most important. The rebuilt engine cannot be ex­
pected to perform properly if parts worn beyond accepta­
ble limits are reused.

BLOCK

i g i
C lean
1. Block in solvent.
2. Block gasket surfaces.
3. Cylinder bores.
4. Oil galleries and passages.
5. Scale deposits from the coolant passages.
In sp ect
1. All expansion plugs for lack of fit or leakage.
2. Valve lifter bores for deep scratches and varnish
deposits.
3. Block for cracks.
— Cylinder walls.
— Coolant jackets.
— Main bearing webs.
— Engine mount bosses.
4. Main bearing bores and main bearing caps.
— All main bearing bores should be rounded and
uniform in ID at all bearing supports.
— The area where the main bearing inserts
contact the main bearing bore should be
smooth.
— If a main bearing cap is damaged and requires
replacement, replace it.
5. Head gasket surface for flatness.
straightedge and feeler gage. Minor irregularities
may be carefully machined. If more than 0.25 mm
(0.010-inch) must be removed, replace the block.
6. Oil pan rail and timing cover attaching area for
nicks. Minor irregularities may be cleaned up with a
flat file.
CYLINDER BORE
I?
In s p e c t
Cylinder bores for scoring or other damage.
M ea s u re
• Cylinder bore taper and out-of-round. Refer to
GENERAL ENGINE MECHANICAL (SEC. 6A).
Cylinder Bore Reconditioning
Refer to GENERAL ENGINE MECHANICAL (SEC. 6A).
PISTON AND CONNECTING
ROD ASSEMBLY
Refer to GENERAL ENGINE MECHANICAL (SEC. 6A)
and perform the following:
❖
D is as s em b le
Components as required.
C lean
Components as outlined.
L*
In sp ec t
Components as outlined.
Use a