How To Pour Crankshaft Main Babbitt Bearings

(Page 2 of 2)

By Bud Motry
November/December 1981
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After it cools twenty minutes, the crankshaft may be jarred loose from its seat. The flanges may be filed to fit with a body file. There is no precise thickness of the flange required as the flywheels may be moved to control end thrust of the shaft. The corners of the bearings must be rounded to fit on the inner side of the bearing with a scraper. This lower half of the bearings should now provide perfect alignment of the crankshaft. It is advisable to check these three factors: (1) the gear teeth clearance, (2) the connecting rod and cap should have sufficient clearance at the base of the housing, depending of course on the size of the engine, (3) the horizontal alignment must permit the crankshaft to be turned freely, 360 degrees, without binding of the connecting rod bearing.

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The next step is to pour the cap bearings. They may be poured one at a time. With one of the crankshaft washers in place to close the opening on the inside of the cap, secure the crankshaft in its new lower bearings with one of the old bearing caps. Cut a shim from asbestos for each side of the bearing. (Note the white appearance of the shim in the photo). This will keep the molten metal from fusing with the already finished lower bearing. Be sure it covers all the new babbitt, extending tightly to the crankshaft. Bolt the cap in place, centering it on the studs. Wedge the washer against the casting with a wood block.

Tip the engine over on its side, supported in a level position by wood blocks. To complete the cap flange, the metal clip used for the lower bearing may be wrapped around the casting and held in place with a 'C' clamp. (Note the clamp in the photo.) The metal form should be level with the flange for the lower half. Heat the bearing cap and the shaft with a torch, plug any pipe thread openings with a block of wood and proceed to pour the bearing. When cooled the cap may be jarred loose with a hammer. Repeat the procedure for the opposite bearing cap and complete the job of shimming and scraping to restore the bearings to last another fifty years.

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