Piston And Connecting Rod Assemblies; Intake And Exhaust Manifolds - GMC 1989 Light Duty Truck Repair Manual

PISTON AND CONNECTING
ROD ASSEMBLIES
Refer to GENERAL ENGINE MECHANICAL (SEC. 6A)
and perform the following:
*
Disassem ble
Components as required.
|m j|
Clean
Components as outlined.
Inspect
Components as outlined.
€
M easure
Piston pin diameter and clearance.
Piston to bore clearance, and fit the pistons.
1. Remove rings from the pistons to be fitted.
• It is not n e c e s s a ry to rem ove th e
connecting rods from the pistons.
• If an excessive amount of varnish or
carbon appears as a ridge at the top of
the cylinder, remove it by scraping or
sanding.
2. Wipe the bores and pistons clean. Select a
piston and rod assembly for the bore to be
fitted and position it down into the bore with
the top of the piston down. The piston should
slide freely through the bore by its own weight
when the piston skirt is 12 to 25 mm from the
top of the block. Use care to make sure the
piston is not damaged when it slides through
the bore. If the piston does not slide through
the bore, it is too tight and another piston
should be selected. Mark the proper piston
and bore for assembly.
3. After a piston has been selected which will
slide freely through the bore, determine if it is
too loose.
• Place a feeler gage (0.060 mm for used
pistons, 0.050 mm for new pistons) at
least 150 mm long and not over 12 mm
wide into the bore with the selected
piston. Hold the feeler gage to the top of
the bore.
• Position the selected piston into the bore
(top down) until the skirt is 12 to 25 mm
from the top of the block. The feeler
gage must be 90 degrees from the piston
pin. If the piston hangs on the feeler
gage and does not fall free, the piston is
correctly fitted to the bore. If the piston
slides freely through the bore, it is too
small and a larger piston is required.
Mark the proper piston and bore for
assembly.
4. When checking more than one bore, it is
possible that a piston that does not fit one
bore will fit another.
*
Assem ble
Components as outlined.
2.8 LITER V-6 6A2-13
Im portant
Each connecting rod and bearing cap should
be m arked, beginning at the front of the
engine. Cylinders 2, 4 and 6 are at the left
bank and, 1, 3 and 5 are the right bank. The
numbers on the connecting rod and bearing
cap must be on the same side when installed
in the cylinder bore. If a connecting rod is ever
transposed from block or cylinder to another,
new connecting rod bearings should be fitted
and the connecting rod should be numbered
to correspond with the new cylinder number.
M easure
m
Ring end gap and ring clearance.
I?
Inspect
• Ring fit.
INTAKE AND EXHAUST
MANIFOLDS
131
Clean
Old pieces of gasket from the gasket surfaces.
Excessive carbon build-up in the exhaust passages
of the intake manifold.
Scale and deposits from the coolant passages of the
intake manifold.
EGR passage of excessive carbon deposits.
Inspect (Figure 18)
1
?
Manifolds for cracks, broken flanges, and gasket
surface damage.
Alignm ent of manifold flanges. Use a straight edge
and feeler gage. If the flanges are out of alignment
by more than 0.1 mm (0.005-inch), the manifold is
warped and should be replaced.