Main Bearing Removal (Without Removing C Rankshaft); Cleaning, Inspection, And Repair; Cylinder Bore - GMC T Series 1994 Repair Manual

3. Crankshaft from the cylinder block with extreme
care, taking care to avoid damage to crankshaft
journals and thrust flange surfaces.
4. Upper main bearing inserts.
MAIN BEARING REMOVAL
(W ITH O U T REMOVING
CRANKSHAFT)
Important
Check the main bearing caps for location markings.
M ark the caps if necessary. The caps must be
returned to their original locations during assembly.
Remove or Disconnect (Figure 22)
Tool required:
J 8080 Main Bearing Remover/Installer
1. Main bearing cap bolts.
2. Main bearing caps.
3. Lower main bearing inserts from the main bearing
caps.

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 section.
These tools (or their equivalents) are specially designed
to quickly and safely accomplish the operations for
which they are intended. They should not be used in
operations for which they are not designed. These spe­
cial tools, when they are properly used, will also mini­
mize possible damage to engine components.
Some precision measuring tools are required for
inspection of certain critical components. These include
micrometers, torque wrenches, feeler gages, dial indica­
tor set, etc. The inspection work, when performed with
the proper methods and tools, is most important. The
rebuilt engine cannot be expected to perform properly if
the parts are worn beyond acceptable limits are reused.
BLOCK
Clean (Figure 23)
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
1. All expansion plugs for lack of fit or leakage.
2. Valve lifter bores for deep scratches and deposits.
3. Cracks in the block.
4. Upper main bearing inserts.
A. Insert J 8080 into the crankshaft oil hole (figure
22
).
B. Rotate the crankshaft to turn the upper main
bearing insert out of the block.
— Cylinder walls.
— Coolant jackets.
— Engine mount bosses.
— Main bearing webs.
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 (figure
24).
A. Set the straight edge on the sealing surface to
be inspected.
B. Take the feeler gage and at various locations,
check the gap between the straight edge and
the sealing surface.
C. If the gap is greater than 0.25 mm (0.010 inch)
at any sealing location, the block must be
replaced.
D. If the gap is less than 0.25 mm (0.010 inch) at
any sealing location and a cause for leakage is
suspected, then the minor irregularities may be
carefully machined from the block.
6. Oil pan, timing cover, and intake manifold mounting
surfaces for nicks. Minor irregularities may be
cleaned up with a flat file.

CYLINDER BORE

Inspect
L *