friesjh

Hello all,

I am currently having the motor rebuilt for my 71 W30 and need a different crankshaft and harmonic balancer for it. The upper end of the motor was still all original, but the crank had been turned at some point and is already at 20 under. I am considering an aftermarket crank if I cannot find a good OEM replacement. The build will be pretty much stock, so I would think a cast crank would be sufficient. Anyone have any experience with aftermarket cranks? I don't want to spend a fortune on a crank. Any suggestions??

cutlassefi

The best one for the money is the one from Eagle. It’s lighter but stronger than a stocker.
However a stock crank will most likely be fine for your application.

Fun71

The crank in my car is .030" under and has been working fine since the last rebuild in the early 90s. Is there some issue about turning a crank more than .020" that I am unaware of?

friesjh

Ken I'm not really sure. I have always been told to look for another crank past 20 under. More chance of spinning a bearing past 20 and since this is a 4 speed car I'd rather be safe than sorry later.

442Harv

I don't see a problem with going 30 under. I was told by one shop I took a crank to, said one of the problems with Olds is because the journals are so large, Look at BBChevy they are smaller than Olds to start out with.

friesjh

I am certainly no expert on the subject, but would think it has more to do with the thickness of the bearing and that larger journals would be a plus not a minus.

cutlassefi

Let me set the record straight here. What happens when guys take a big block Olds Crank and offset grind it to stroke it for use with a smaller BBC rod? The answer is nothing.
The steel bearing shell is the same thickness on a std and .010 bearing. Then they increase that thickness to accommodate the .020 and .030’s. Not sure what they do with .040s, but I know the Babbit and Tin layers stay about the same for all. This is per an engineer at Clevite.
Grind it, you’ll be fine.