Turn the rod front-to-back and repeat step (c), above. The total difference in the indicator readings must
not exceed 0.008 inch (0.20 mm)without the piston pin bushing, or O.004inch (0.10 mm)with the bushing
installed and bored to size. The length must be within tO.001 inch (±O.03 mm) on the gages. Replace
defective connecting rods.
Measure the rod twist with a feeler gage between the piston pin and dial holding plate. When the rod does
not contain a piston pin bushing, the twist must not exceed 0.020 inch (0.51 mm). The twist must not
exceed 0.010 inch (0.025 mm) with the bushing in place and bored to size. Replace defective connecting
Replace a worn piston pin bushing (13, Figure 9-24) as follows:
To ensure proper alignment of the piston pin bushing during installation, the connecting rod
bore must be chamfered before the old bushing is removed. If the connecting rod bore has
been previously chamfered, omit steps (a) through (i), below.
Install guide bushing ST-861-2 (1, Figure 9-27) on the chamfering tool ST-861 (2).
Extend the adjusting screw holder (3) to its longest position (third notch).
Loosen the setscrews (4) and move the tool bit (5) toward the chamfering tool (2).
Loosen the setscrew (6) and turn the adjusting screw (7) in until it extends below the top edge of the tool bit
Move the tool bit (5) toward the adjusting screw (7) until the cutting edge of the tool bit just dears the
adjusting screw. Lock the tool bit in this position with the setscrews (4), and install the assembly in the
connecting rod (8) piston pin bore.
Back out the adjusting screw (7) until the cutting edge of the tool bit (5) just contacts the edge of the bore
of the connecting rod (8). Lock the adjusting screw in position with the setscrew (6).
Hold a slight downward pressure on the chamfering tool (2), and use a ratchet wrench to turn the
chamfering tool one complete turn.
Remove the chamfering tool assembly, install it in the opposite side of the connecting rod pin bore, and
repeat step (g), above.
Repeat steps (f) through (h), above, until a uniform pin bore chamfer of 0.040 to 0.060 inch (1.02 to 1.52
mm) deep is achieved on both sides of connecting rod.
1. GUIDE BUSHING (ST-861-2)
2. CHAMFERING TOOL (ST-861)
3. ADJUSTING SCREW HOLDER
5. TOOL BIT
7. ADJUSTING SCREW
8. CONNECTING ROD
Figure 9-27. Chamfering Connecting Rod Piston Pin Bore Using ST-861