Cleaning, Inspection And Repair; Block - Chevrolet 1991 Light Duty Truck Repair Manual

6A3-10 4 .3 LV 6 ENGINE
1. Main bearing cap bolts.
2. Main bearing caps.
3. Lower main bearing inserts from the main bearing
caps.
4. Upper main bearing inserts.
• Insert J 8080 into the crankshaft oil hole (figure
14).
• Rotate the crankshaft to turn the upper main
bearing insert out of the block.

CLEANING, INSPECTION AND REPAIR

A solvent tank large enough to hold the larger engine
parts will be needed, as well as various bristle brushes
and gasket scrapers. A source of compressed air will
also be helpful in the cleaning operations.
Special tools are listed and illustrated throughout this
section, with a complete listing at the end of the sec­
tion. These tools (or their equivalents) are specially
designed to quickly and safely accomplish the opera­
tions for which they are intended. They should not be
used in operations for which they are not designed.
These special tools when they are properly used, will
also minimize possible damage to engine components.
Some precision m easuring tools are required for
inspection of certain critical components. These include
micrometers, torque wrenches, feeler gages, dial indi­
cator set, etc. The inspection work, when performed
with the proper methods and tools, is most important.
The rebuilt engine cannot be expected to perform prop­
erly if the parts are worn beyond acceptable limits are
reused.

BLOCK

Clean
1. Block with solvent.
2. All traces of old gaskets.
3. Cylinder bores.
4. Threaded holes.
5. Oil galleries and passages.
6. Scale deposits from coolant passages.
L*
Inspect
All expansion plugs for lack of fit or leakage.
Valve lifter bores for deep scratches and deposits.
Cracks in the block.
— Cylinder walls.
— Coolant jackets.
— Engine mount bosses.
— Main bearing webs.
Figure 14— Removing the Main Bearing Insert
4. Main bearing bores and caps.
— All main bearing bores should be rounded and
uniform in ID at all of the bearing supports.
— The area were the main bearing inserts contact
the main bearing bore should be smooth.
— If a main bearing cap is found to be damaged,
replace the cap and line bore the block.
5. Cylinder head mounting surface for flatness, using
a precision straight edge and feeler gage.
• Set the straight edge on the sealing surface to
be inspected.
• Take the feeler gage and at various locations,
check the gap between the straight edge and
the sealing surface.
• If the gap is found to be greater than 0.25 mm
(0.010-inch) at any sealing location, the block
must be replaced.