Pistons and Connecting Rods – Disassemble and Assemble


Disassembly Procedure

Remove the pistons and the connecting rods. Make a temporary mark on the components of the piston and connecting rod assembly. This will ensure that the components of each piston and connecting rod assembly can be reinstalled in the original cylinder. Mark the underside of the piston on the front pin boss. Do not interchange components.


Remove:
- the two setscrews (12) and the connecting rod cap (11) from the connecting rod (6). Discard the setscrews. Fracture split connecting rods should not be left without the connecting rod caps installed. After the disassembly procedure for the piston and connecting rod is completed, carry out the assembly procedure and the installation procedure as soon as possible.
- the lower bearing shell (10) from the connecting rod cap (11).
- the upper bearing shell (9) from the connecting rod (6). Keep the bearing shells together.


Place the piston and connecting rod assembly on a suitable surface with the connecting rod upward. Use Tooling in order to remove the circlips (5). The forged marks (X) may be on the front of the connecting rod assembly, or on the rear of the connecting rod assembly. The forged marks should not be used for the purposes of orientation.
- the piston pin (8) and the connecting rod (6) from the piston (4). If the piston pin cannot be removed by hand, heat the piston to a temperature of 45 ± 5 °C (113 ± 9 °F). Do not use a torch to heat the piston. Note the orientation of the connecting rod (6) and the piston (4). Place the piston on a suitable surface with the crown upward.
- the compression rings (1) and (2), and the oil control ring (3) from the piston (4). Identify the position and orientation of the compression rings (1) and (2), and the oil control ring (3). Inspect the connecting rod for wear or damage. If necessary, replace the connecting rod (6) or replace the bush for the piston pin (7). If the connecting rod or the bush for the piston pin are replaced, first identify the height grade of the connecting rod.
Repeat Steps to disassemble the remaining pistons and connecting rods.

Assembly Procedure

Ensure that all components are clean and free from wear or damage. If necessary, replace any components that are worn or damaged.
If the original piston is assembled, follow Steps to install the piston rings.
Position the spring for the oil control ring (3) into the oil ring groove in the piston (4). The central wire must be located inside the end of the spring.


Use Tooling to install the oil control ring (3) over the spring. Ensure that the central wire is 180 degrees from the ring gap.
Use Tooling to install the intermediate compression ring (2) into the second groove in the piston (4). The word “TOP” must be upward. The chamfer on the inner face must be downward.
Use Tooling to install the top compression ring (1) into the top groove in the piston (4). The word “TOP” must be upward.
Position the piston ring gaps at 120 degrees away from each other. A new piston assembly is supplied with new piston rings.
If the connecting rod assembly (6), (7), (11) and (12) or the bush for the piston pin (7) is replaced, ensure that the height grade of the connecting rod is correct.


Lubricate the bush for the piston pin (7) in the connecting rod and lubricate the bore for the piston pin in the piston (4) with clean engine oil.


Place the piston on a suitable surface with the crown downward.
Install:
- the connecting rod (6) and the piston pin (8) to the piston (4). Ensure that the square (13) on the piston, and the slot (14) on the connecting rod are in the correct position. See illustration. If the piston pin cannot be installed by hand, heat the piston to a temperature of 45° ± 5°C (113° ± 9°F).
- the circlips (5) to the piston pin bore in the piston (4). Ensure that the circlips are seated in the grooves in the piston.
- the upper bearing shell (9) into the connecting rod (6). Ensure that the locating tab for the upper bearing shell is correctly seated in the slot in the connecting rod.
- the lower bearing shell (10) into the connecting rod cap (11). Ensure that the locating tab for the lower bearing shell is correctly seated in the slot in the connecting rod cap. Repeat Steps for the remaining piston and connecting rod assemblies.
- the pistons and the connecting rods.