View Full Version : pilot bushing options for 75 455

04-12-2007, 11:13 PM
trying to put a 4 speed behind a 75 455. i know there's a problem when it comes to getting a pilot bushing in there. i read a post on here about dick miller racing and him having one that works. i looked on his site and didn't find anything. anyone have one, and having good luck with it? can i just get a bushing machined to specs? looking for some options here..motor is assembled so i dont think taking it apart to get crank machined is what i want to do..thx

04-13-2007, 03:34 AM
Check your block for the stud boss hole on the driver's side. I don't think the 75-6 block have this hole since no 4 speeds were offered in those years.
I don't think you can machine the crank w/o removal since you need to have snap ring groove installed to retain the pilot bushing unless someone has one that is a press-fit.

04-13-2007, 06:26 AM
I went thru this on an Olds.

The adapter bearing is used on cranks that do not have the correct hole machined. It is a press fit into the converter snout hole.

Well, the one I used failed - it spun in the O.D., and it was a tight press fit.

Drilling the crank in the car is harder than Chinese arithmetic.....:Dou:

My advice is to have the crak machined correctly.

The Olds press fit bearing is BCA 7109

04-13-2007, 07:15 AM
In this case have the pilot bearing O.D. turned down to match your crank. It has recently came to light the after market BBC bearing may be just a touch to large of an outside O.D. The difference is not much, I believe the dimension is in the U-Shift-Em section. Use a Brass type bearing and not the roller type.

I am not shure if the cranks intended for 4 speed applications were cleaned up just a touch (as all of the ones I have seen were drilled) or a Buick pilot bushing was a different size (smaller O.D.) than a Chevy and the aftermarkets close enough theroy is causing problems. Not everyone has had the problem, but a enough people have to see this as a potential concern.

I still find it hard to believe that when the engine was being assembled they knew which trans it was to be matched to though.

It seems the larger O.D. being pressed in the smaller opening distorts the I.D. of the bearing and not allowing the trans input shaft to slide thru.

04-13-2007, 09:30 AM
Check your block for the stud boss hole on the driver's side. I don't think the 75-6 block have this hole since no 4 speeds were offered in those years.

I'd check the block regardless. My block is a 73-74 and it had no provisions for the block stud. Drilling and tapping the hole with engine in car was quite interesting.:Dou:

04-13-2007, 03:28 PM
Dunno if this helps. But I just swapped the clutch on the BBB Chevy 4X4. While I was in there, I pounded in a new GM roller pilot bearing. Fit great. Crank is 69 430.

Rich Johns
04-13-2007, 04:54 PM
I too have a fully built 75 455 that I want to put into my 70 GS 455 4 speed car for a while.
Keep me posted on what you conclude to make this year motor work under 4 speed application

04-13-2007, 05:22 PM
I used a roller bearing from a sbc or bbc I believe they are all the same size. I then made my own hyd cluch set up so I didn't need to worry about the stud boss hole stuff. Hope that helps!

04-14-2007, 11:52 AM
Both my '70 and '73 blocks were drilled and tapped for the stud. They were both engines out of big cars. My '76 blue block was also out of a big car and it is drilled only, not tapped. ?!?!