I am looking for the technical details of a manual trans swap when NOT drilling the crank out to do it the factory way. I want to know how everything fits, measurements and pictures would be nice, when using a factory bellhousing and 4 speed. Ive seen the drill specs and it seems as if the pilot bearing in a factory setup sits in the crank about a .5" so Im assuming the splined part of the input shaft actually protrudes into the crank in the bigger outer recess. Im wondering how this works, assuming the input shaft actually does go in that far, when using an adapter bushing in the outer recess? Ive heard of cutting the input a little so it doesnt bottom out in an undrilled crank but assume its just the small part that rides in the pilot.

 

You are correct. An undrilled automatic trans crank does not have a deep enough recess to clear the input shaft of the manual trans. When using the conversion pilot bearing that fits in the AT converter snout recess in the crank, your options are to cut 1/2"-3/4" off the tip of the manual trans input shaft or to drill a clearance hole in the end of the crank. Since you are using a conversion bearing that locates in the converter pilot hole, the clearance hole does not need to be precisely concentric the way it would have to be if you were running a stock pilot bearing. As a result, folks have successfully drilled this hole with the crank in the engine. It is not easy to do, but it can be done. Don't drill any deeper than 3/4". The hole needs to be slightly larger in diameter than the tip of the input shaft to allow clearance.

 

I went the conversion bearing route first.....

Drilling the crank is unbelievably difficult. The material is hard like a diamond.

It took Steve Minore (Stick W31) about an hour to drill a clearance hole about 1/2" deep. That was using a $75 drill bit and a 3/4 hp drill motor.

The conversion bearing I got was from Dick Miller racing. It was a 100% pure chineseum piece of excrement.

Anyway, I did the conversion.

It was difficult to impossible to shift into reverse. The reason was the I.D. that the conversion bearing fit into was out of concentricity.

The conversion bearing failed after about 500 miles.

So, I pulled the engine and had the crank drilled properly for a 7169 bearing.

It now works flawlessly.

Moral of the story: Do it right the first time.

BTW - the manual conversion is worth every penny. The Muncie whine is music to my ears......

 

I'm not using a conversion bearing/bushing, I got an oilite bushing, dorman I think, that is made to fit into a chevy that originally had a turbo glide and its a nice tight fit. I'm just concerned about the splined portion going into the crank far enough.

 

I know the auto crank conversion works, I just want to know the the relation of the splined portion of the crank to the bushing? Is it only the input that rides in the bushing that becomes a problem In this conversion?