Dismantling
1. Remove the bearing inserts from the connecting rod and cap.
2. Mark the pistons and pins to assure assembly with the same rod and installation in the same cylinders from which they were removed.
3. Remove the piston pin from the piston and con-necting rod (Fig. 74). Remove the piston rings.
PISTONS, PINS AND RINGS
Cleaning
Remove deposits from the piston surfaces. Clean gum or varnish from the piston skirt, piston pins, and rings with solvent. Do not use a caustic cleaning solution or a wire brush to clean pistons. Clean the ring grooves with a ring groove cleaner (Fig. 76). Make sure the oil ring slots (or holes) are clean.
Inspection
Carefully inspect the pistons for fractures at the ring lands, skirts, and pin bosses, and for scuffed, rough, or scored skirts. If the lower inner portion of the ring grooves has a high step, replace the piston. The step will interfere with ring operation and cause excessive ring side clearance.
Spongy, eroded areas near the edge of the top of the piston are usually caused by detonation, or pre-ignition. A shiny surface on the thrust surface of the piston, offset from the centreline between the piston pin holes, can be caused by a bent connecting rod. Replace pistons that show signs of excessive wear, wavy ring lands, fractures, and/or damage from detonation or pre-ignition.
Check the piston to cylinder bore clearance with a tension scale and ribbon, following the procedure under Fitting Pistons in this section. Check the ring side clearance following the procedure under Fitting Piston Rings in this section.
Replace piston pins showing signs of fracture or etching and/or wear. Check the piston pin fit in the piston and rod. Refer to Fitting Piston Pins” on pages 49 and 50.
Replace all rings that are scored, chipped, or cracked. Check the end gap and side clearance. It is good practice to always install new rings when overhauling the engine. Rings should not be transferred from one piston to another regardless of mileage.
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 e CONNECTING RODS
Cleaning
Remove the bearings from the ‘rod and cap. Identify the bearings if they are to be used again. Clean the con-necting rod in solvent, including the rod bore and the back of the inserts. Do not use a caustic cleaning solution. Blow out all passages with compressed air.
Inspection
The connecting rods and related parts should be care-fully inspected and checked for conformance to speci-fications. Various forms of engine wear caused by these parts can be readily identified.
A shiny surface on the pin boss side of the piston usually indicates that a connecting rod is bent or the piston pin hole is not in proper relation to the piston skirt and ring grooves.
Abnormal connecting rod bearing wear can be caused by either a bent connecting rod, an improperly machined crankpin, or a tapered connecting rod bore. Twisted connecting rods will not create an easily identi-fiable wear pattern, but badly twisted rods will disturb the action of the entire piston, rings, and connecting rod assembly and may be the cause of excessive oil con-sumption.
Inspect the connecting rods for signs of fractures and the bearing bores for out-of-round and taper. If the bore exceeds the recommended limits and/or if the connecting rod is fractured, it should be replaced.
Check the ID of the connecting rod piston pin bore.
Replace the connecting rod if the pin bore is not within
dimensions given in Data Section under “Connecting
Rod”.
Replace defective connecting rod nuts and bolts.
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