I am having a crank drilled for a manual transmission. Should i stay with the factory size or is there a better alternative? My main concern is availability and quality. I don’t want to be in a position where I won’t be able to find a replacement years down the road.

 

I've used both the bearing and bushing. I know the factory used the bearing. But it appears to me the bushing would require less maintenance.

 

On one of the Chevy websites I frequent a lot of guys like the bushing better and claim the bearing will fail after a while. They are not expensive so buy and extra.

 

BCA7109 is the correct bearing.

That is what I use.

 

That bearing is too large for my 455 crank. Do you have a solution for that other than having the bearing machined? Part number for the bushing?

 

X2 on bushing requiring less maintenance. If a no machining needed bushing is available I'd use that.

Good luck!!!

 

oletrux, are you changing from an automatic trans to a manual trans? If so, the Oldsmobile automatic transmission crankshaft must be at the least drilled deeper to accommodate the length of the manual transmission input shaft. The correct way, although more expensive, is to have a machine shop machine the crankshaft for the 7109 bearing as was done from the factory for manual shift applications. You can also buy a conversion bushing from some vendors such as https://dickmillerracing-com.3dcartstores.com. If using the bushing you must still drill the end of the crankshaft deeper for clearance of the manual trans input shaft as mentioned above. Using the search feature, you will find on this site the specifications for machining the crankshaft for the 7109 pilot bearing.

 

Wouldn't machining the crank for a pilot bearing make the crank unusable for an auto trans unless it is bushed back to original diameter? This might make a bushing a better choice.

 

Lot's of misinformation on this post.

Most Olds BB cranks were not drilled for manual transmissions.

If you want to convert to a manual, you have to do one of two things:
1. Install a conversion bearing which uses the recess for the torque converter nose. You will
have to either drill out clearance at the crank OR cut the transmission input shaft. The crankshaft is harder than diamonds to drill.

2. Using the Mondello Technical manual, have the crank drilled for a BCA7109 bearing, which is what the factory used.

You can drill the crank for a Chevy type bushing as well.

I went thru this whole effort after a conversion bearing install failed. Do it right the first time.

 

Thanks guys. This is an upgrade from my 403 to a 455. I've been down this road before so I'm familiar with the clearance issues. If my measurements are accurate, it's OK. The 5-speed uses a 1/4" spacer plate between the TKO and the bell housing to make room for the snout.
I am just looking for an easier way to get the pilot bearing to fit since redrilling the crank is not practical, at all. I'll take a look at that adapter bearing. Thanks again.

 

Sugar, machining the crankshaft for a manual trans pilot bearing does not render it unusable with an automatic trans. It will still have clearance for the snout of the torque converter.

 

Wouldn't the machined crank be too large to center the converter?

 

No.

 

^^Holy Guacamole^^ You have some awesome historical engineering documentation.

 

Nice...thanks Joe!