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Align Boring Case

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10/15/02*

Answer >  No I don't think they screwed up your case, they just failed to true the cam tunnel when they did the align bore. When the case gets to hot or when an engine is turned at very high rpm the main bearings get loose in the case, so align boring is needed. At the same time the bearings are moving around in the case, the two halves of the case are working against each other, and as they rub away material they are actually coming closer together by a small amount. The old came bearings wore at approximately the same rate so the cam turned freely. But when you align bored the case and installed new cam bearings, the case smashed the cam bearings tight agents the cam. The correct way is to true the cam tunnel each time the case is align bored. The Photo shows the tool in place. Note the dark lines in the center of the main bearing surface. If you run your fingernail across this surface you can tell if the case needs boring. If your nail catches on the dark line, then you have at least .003" wear and the case must be bored for over size bearings. You must also check that the bearing flange on the flywheel end, has no end play when installed. (If the case dia. is very loose, it is more then likely the thrust must be cut.) Once the bearings start to get loose in the case they wear at a very fast rate, so if not taken care of quickly the case can be ruined. Vic.

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