Piston Selection (All Except 2.5L And 2.8L Engines) - Chevrolet 1991 Light Duty Truck Repair Manual

6A-8 GENERAL ENGINE MECHANICAL
PISTON SELECTION
(ALL EXCEPT 2.5L
AND 2.8L ENGINES)
1. Check the used piston to cylinder bore clearance.
| Measure (Figures 11 and 12)
• Cylinder bore diameter. Use a telescoping bore
gage, located 65 mm (2 1/2-inches) below the
top of the cylinder bore (figure 11).
• Piston diameter. Measure the piston skirt at a
right angle to the piston pin, at the centerline of
the piston pin (figure 12).
• Subtract the piston diameter from the cylinder
bore diameter to determine piston to bore clear­
ance.
• Refer to " Specifications" in the proper section.
Determine if the piston clearance is in the
acceptable range.
2. If the used piston is not acceptable, determine if a
new piston can fit the cylinder bore.
3. If a new piston does not bring the clearance within
tolerances, the cylinder bore must be recondi­
tioned.
4. Mark the piston to identify the cylinder for which it
was fitted.
Figure 11—Measuring Cylinder Bore Diameter
Figure 12—Measuring the Piston Skirt
A. 65mm (21 /2-inches)
B. Cylinder Bore
B5073
B9447
ASSEMBLY
Assembling the Piston and Connecting Rod (All
except 6.2L Engines)
|n%-| Assemble (Figure 13)
Tool Required:
J 24086-B Piston Pin Remover and Installer Set
1. Piston and connecting rod.
• The piston and connecting rod must be
installed in the proper position.
— 2.5L Engines: The raised notch side of the
connecting rod must be opposite the notch
in the piston crown.
— 2.8L Engines: The bevel on the connecting
rod should face the outside of the engine.
— All Others: The valve cutouts in the piston
crown must be opposite the connecting rod
bearing tangs.
• Lubricate the piston pin holes in the piston and
connecting rod with engine oil.
• Install the pin guide (item E, figure 13) to hold
the piston and connecting rod together. Be sure
to use the proper pin guide. Refer to the
instructions supplied with the tool.
2. Piston pin.
• Insert the piston pin into the piston pin hole.
• Place the assembly on the support fixture (fig­
ure 13).
B. Adjustable Installer J-24086-9
C. Support Fixture J-24086-20
D. Connecting Rod Support J-24086-11
E. Pin Guide
F. Lock Ring
G. Adjuster
H. Number Scale
Figure 13—Installing the Piston Pin
B5076