Hey all, my apologies if i missed a thread about this, but I'm thinking of swapping out the TH350 in my 1968 Cutlass with a Tremec TKX 5 speed. My engine is the stock Rocket 350, without the hole for the input shaft and pilot bearing. Since I'm drilling the crank, and starting from scratch, is it better to go with the bronze bushing that Chevrolet used, or use the BOP pilot bearing, which I guess is the #7109? Thanx in advance for your replies!

-Karl

 

I vote "no, don't do it". I was never able to get it right. A properly drilled crank is the only way to fly. IF you do venture down the path, measure carefully. I never did confirm it, but I believe the shoulder on the input shaft needs to be slightly deeper than the face of the crankshaft flange. It's close, but wipes the thrust bearing face out rather quickly if not done correctly. Then, you're in for a rebuild. It's good if you're looking for an excuse. It's bad if you think you're going to get away with an easy manual transmission swap. Tread lightly, my friend.

 

I have about 4500 miles on my 455/ muncie build using the conversion bearing with no issues so far. You will still need to drill the crank to get clearance for the end of the input shaft or cut down the end of the shaft.

 

When you say you are "drilling the crank", do you mean pulling the crank and having a machine shop bore the hole?

 

Yep, I'll pull the crank and have it drilled for either the BOP bearing, or Chevy bushing. I'm seeing more posts that I missed on this subject, and the more I read, I'm leaning towards getting the BOP bearing. I'll use your blue prints on the hole dimensions as a guide.

https://classicoldsmobile.com/forums...ations-190692/

-Karl

 

If you're getting it done correctly, do it correctly. Bearings aren't really necessary; bushings work fine.