Cleaning, Inspection, And Repair; Block - GMC 1990 Light Truck Repair Manual

6A2-12 2.8 LITER V
Figure 17—Removing or Installing the Main
Bearing Insert

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

Clean
1. Block in solvent.
2. Block gasket surfaces.
3. Cylinder bores.
4. Oil galleries and passages.
• Remove the oil gallery plugs.
5. Scale deposits from the coolant passages.
{ J l Inspect
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.
-6
— 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. Deck surface for flatness. Use a 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.
7. Transmission case mating surface.
Important
• If the transmission case mounting surface is
not flat, a broken flexplate may result.
CYLINDER BORES
Inspect
• Cylinder bores for scoring or other damage.
Measure
Cylinder bore taper and out-of-round. Refer to
GENERAL ENGINE MECHANICAL (SEC. 6A).
Cylinder Bore Reconditioning
Refer to GENERAL ENGINE MECHANICAL (SEC. 6A).