How to Rebuild Your Nissan & Datsun OHC Engine by Tom Monroe

Author:Tom Monroe [Monroe, Tom]
Language: eng
Format: azw3, mobi, epub
Publisher: California Bill's Automotive Handbooks
Published: 2002-05-30T16:00:00+00:00

DISASSEMBLING & ASSEMBLING PISTONS & CONNECTING RODS

Disassembling or assembling connecting rods and pistons is a job for an expert with the proper equipment. If you are replacing the pistons, the rods and pistons must part company. Only one method can be used to do this correctly. The wrist pin must be pressed—not driven—out of the small end of the rod. It is held in place by a 0.0006–0.0014 in. (0.015–0.035mm) interference fit. A press with mandrels to back up the piston and bear on the pin is required.

You can assemble a connecting rod and piston one of two ways. The first is done by carefully reversing the disassembly process. The other method, and the one I prefer, is the heating method. This is done by simply heating the small end of the connecting rod with a torch or a special electric heater. This expands the pin hole, allowing the pin to slide into place without need of a press. Pin and piston have to be fitted to the rod very quickly while the rod is hot, before the rod and pin approach the same temperature. Otherwise, the pin will be trapped by the interference fit before it’s in position. A press will then be required to complete pin installation.

If you are assembling your own pistons and rods, be aware of the piston’s location relative to its connecting rod. As installed in the engine, pistons usually have a notch at their front edge or an arrow stamped in the dome, either of which must point to the front of the engine when installed. Also, connecting-rod numbers must face toward the distributor or left side, of engine. The reasons for this are: The wrist pin is offset in the piston toward the thrust side of the cylinder bore about 0.040 in. (1mm). This reduces piston noise by preloading the piston against the cylinder-bore side that’s opposite crankshaft rotation. Also, the connecting-rod squirt hole must point at the thrust side of the bore so the piston and bore will receive proper lubrication.

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