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REAR MAIN BEARING CLAMPING SPACER:

The removal and reinstallation of the rear main roller bearing of many Austin 7 engines often results in the inner bearing track becoming a loose fit on the crankshaft journal. This looseness then allows the rotating crankshaft to slip within the inner bearing track and can cause significant wear of the crankshaft journal. The worn journal will permit its sloppy bearing to move about freely while the engine is running, contributing to unnecessary crankshaft flexing and fatigue.

Several repair schemes have been devised including coating of the surfaces during assembly with a Locktite retaining compound. This appears to successfully hold the bearing in place, however the specifications for most Locktite grades show that they suffer from thermal ageing and, although they have an indefinite service life at temperatures around 20 degrees Celsius, it can be reduced significantly when continuously subjected to the temperatures encountered on the crankshaft. Relying on a Locktite compound alone means relying too much on hope, if the engine is to remain in service for an extensive period.

A modification has been devised that positively holds the bearing in place on the crankshaft journal by using the flywheel to clamp the inner bearing track as the crankshaft nut is tightened. A spacer inserted between the bearing and the flywheel boss takes up the normal clearance but must be of the correct thickness, too thick a spacer will not let the flywheel and the crankshaft tapers meet correctly whereas too thin a spacer will be ineffective.

The spacer depicted overcomes the limitation of the fixed thickness spacer because it will compress but will not yield.

To establish the correct spacer thickness the crankshaft nut was torqued to 80 ft lb. with a feeler inserted between the bearing and the flywheel boss. As an 0.082 inch. feeler provided the correct nip the spacer dimensions for this feeler thickness are shown.

DENNIS HOURIGAN