Buick 300 Crankshaft Pilot Bushings

as published in British V8 Newsletter, Volume XII Issue 2, May 2004

by: Dan LaGrou and Kurt Schley

The use of the 1964 - 67 Buick 300ci crankshaft to stroke a Buick/Olds 215 aluminum V8, or one of its Rover V8 descendants, is relatively common. Also common is encountering a problem if the stroked motor is mated to a manual transmission such as a T5 5-speed. The dilemma is with the pilot bushing fit. It may not be possible to install a stock dimensioned bushing into the crankshaft.

The stock pilot bushing is sized for a press fit into a 1.090" bore in the end of the crank. Buick bored the pilot bushing bore to this dimension only if the crankshaft was actually destined for a manual transmission equipped Buick. The crankshafts bored to 1.090" exhibit a well defined step near the back of the bore. If the destination car was one of the much more common automatic transmission models, the boring procedure was not performed and the step in the bushing bore is less prominent. This omission left a pilot bushing bore of around 1.050", thus precluding the installation of a stock dimensioned pilot bushing.

Buick 300 Crankshaft Pilot Bushing

Fortunately, if you are utilizing one of the un-bored crankshafts and intend it for manual transmission service, the solution to fitting a pilot bushing is not overly complicated.

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Option one is to set the crank up in a horizontal mill or lathe and drill/ream the pilot bushing bore out to 1.090". The 1.090" dimension will provide for a 0.002" interference fit between the crankshaft bore and the bushing O.D. This option is necessary if you plan on using one of the needle-roller pilot bearings available from Summit Racing and other high performance parts suppliers.

The second (much easier) option is to have the O.D. of the pilot bushing turned down to fit the existing bushing bore in the crankshaft. Be sure to measure the crankshaft bore with a telescoping gauge and a 1 - 2" micrometer to check its actual dimension. Machine the bushing O.D. for the 0.002" interference fit.

The above information is applicable to the use of a GM manual transmission. If the 300 crank is being mated to a Ford T-5, an additional machining step is required. The stock style GM pilot bushing has a 0.590" I.D. The input shaft diameter for a V8 style Ford T-5 requires a 0.670" pilot bushing I.D., so the GM bushing will require boring to this dimension.

Disclaimer: This page was researched and written by Dan Lagrou and Kurt Schley. Views expressed are those of the authors, and are provided without warrantee or guarantee. Apply at your own risk.

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