The crank in my '56 engine is only partially drilled and the stock pilot bushing I need to run the Muncie won't fit. Since the engine is a runner, I'd rather not pull the crank to have it drilled. Is it possible to just turn down the bushing on a lathe so that it fits? From what I've measured, the depth is not an issue for the input shaft.
Is it the stock bushing for the Muncie or the stock bushing for the olds? If its not for the olds then I would look for the olds pilot bushing and check for fit on the inside for the trans.
It's the stock one for the Muncie, but I believe it's the same as the stock Olds (it was for my '54 engine). The difference here is that in '56, the cranks were only drilled for pilot bushings if the car came with a manual transmission. As far as I know, the one I have came with a Jetaway (automatic). The part number for the pilot bushing on these Olds is the same, '49-58...maybe even later.
From the picture of the crank it doesn't look like you have a lot of area to even get a pilot bushing seated in it.
I had a 455 Buick that was the same way. No matter what I did it just wasn't gonna work right. I ended up taking the crank and getting it drilled. I was so tempted to try and drill it myself but was to scared it screw it up. Probly would have worked fine but I didn't want to destroy the crank.
For later model engines they make a ball bearing in a holder that bolts onto the flywheel bolts. Wonder if they make one that will fit your engine?
Been a long long time, but IIRC I machined an aluminum ring to press into the larger diameter crank hole. The ring had an I.D. machined to press-fit a stock Chevrolet bronze pilot bushing. I think the Chevrolet bushing was shortened slightly. This was done to fit a Muncie 4 spd and an aftermarket aluminum adapter to the Olds. You have to measure the input shaft to be sure that the shoulder(spline) of the trans doesn't bottom against the pilot bushing when you bolt up the trans.
I did this a long time ago when I put a Dodge three-speed against a '55 270 hemi from a Powerflight car. Turned it down until I had a slight interference fit and tapped it in. It worked fine for me, and it should for you as long as there is enough "meat" left on the bushing.
I would turn a shoulder on the Muncie bushing, so you get the full length of the bushing. The press-in length looks about 5/16" from your picture. It should be enough, I'd go for it. The trick is accurately measuring the diameter in the crank.
There was an issue with the SBC engines of the mid/late 50's that used an automatic, and when a stick was bolted to them a "special" pilot bushing was needed; had to do with how the cranks were machined. Maybe start with one of those pilot bushings, modified to work. I've forgotten the particulars, but maybe someone else will remember more. I am Butch/56sedandelivery.
When you say "partially drilled", are you referring to depth or diameter? How does the stock pilot bushing compare, in size, as to what you have measured, in the crank ?
The Jalopy Journal
