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SERIES 55 PISTON AND CONNECTING ROD ASSEMBLY

Since the piston and connecting rod assembly is composed of two separate components, each component will be discussed in greater detail in its own section. ‪

Repair or Replacement of Piston and Connecting Rod

To determine if repair is possible or replacement is necessary, perform the following procedure. See Figure 21779 . ‪

Repair or Replacement of Piston and Connecting Rod Flowchart

Removal of Piston and Connecting Rod

Pre-cleaning is not necessary. ‪

Remove the piston and connecting rod assembly as follows: ‪

  1. Drain the engine cooling system. Refer to section .
  2. Drain the engine oil. Refer to section .
  3. Remove the oil pan. Refer to section .
  4. Remove cylinder heads. Refer to section .
  5. Using an emery cloth, remove any carbon deposits from the upper surface of the cylinder liner.
  6. Remove the bearing cap and lower bearing shell from the connecting rod.
  7. Push the piston and connecting rod assembly out through the opening in the top of the cylinder block.
  8. After the piston and connecting rod assembly are removed, reassemble the bearing cap and lower bearing shell to the connecting rod. If they are not already marked, match-mark the rod and cap on the tang side with number of the cylinder from which they were removed. This will ensure they are reinstalled in the proper cylinder. See Figure 25427 .

    Connecting Rod and Cap Identification

    Note: If removing the piston and connecting rod assembly to access the cylinder liner, stop here. Refer to section .for cylinder liner removal procedure.

Disassembly of Piston and Connecting Rod Assembly

Piston assembly components should be kept segregated by cylinder and match-marked during disassembly to ensure they are reassembled in the proper position. ‪

NOTICE:

Do not stamp cylinder numbers on components. Stamping may damage the components. ‪

Use a paint pencil to mark the components with the appropriate cylinder number. ‪

Disassemble the piston and connecting rod as follows: ‪

  1. Remove the piston pin retaining rings and piston pin.
  2. Separate the piston from the connecting rod.
Inspection of Piston and Connecting Rod Assembly

Refer to section for disassembly and inspection procedures for the piston and piston rings. ‪

Refer to section for disassembly and inspection procedures for the connecting rod. ‪

Installation of the Piston and Connecting Rod Assembly

Install the piston and connecting rod assembly as follow: ‪

  1. Attach the connecting rod to the piston with the longest part of the connecting rod end facing the camshaft side of the engine.

    NOTICE:

    Whenever pistons are reused, new piston pin retaining rings must be installed. ‪

  2. Install retaining rings on the piston pin.
  3. Lubricate the piston with clean engine oil.
  4. Position piston rings, with their gaps offset approximately 180 .
  5. Install piston and connecting rod assembly into tool J 41328.
  6. Install J 41328 and tighten until the rings assume the piston diameter.
  7. Place the bearing shell in the connecting rod, making sure the tang fits in the groove. Lubricate the bearing shell with clean engine oil.
  8. Insert the piston and connecting rod assembly into the cylinder liner. See Figure 25461 .

    1.Installation Subassembly ‪

    3.Cylinder Block ‪

    2.Piston and Connecting Rod Assembly ‪

    Installation of Piston and Connecting Rod Assembly

    NOTICE:

    Always measure connecting rod cap bolts before reusing and replace with new belts, if required. The maximum length of reusable bolts is 68.5 mm (2.70 in.). Reusing bolts that are stretched beyond this limit may result in bolt loosening or breakage during engine operation, which may cause severe engine damage. ‪

  9. Assemble the connecting rod bearing cap, and screw the bolts in manually.
  10. Torque the bolts 100 N m (74 lb ft).
  11. Turn bolts an additional 90100 degrees.
  12. Check the connecting rod axial clearance. Allow a maximum of 0.292 mm (0.0115) and a minimum 0.13 mm (0.0051in.).
  13. Position the piston at top-dead-center, and measure its protrusion above the cylinder block. Take two measurements at opposite sides of the piston. The average of these two measurements must fall within 0.43 to 0.07 mm (.0169 to .0028 in.). If the measurements are not met, replace the pistons. Refer to section .