B crank in an A

[jfreddy]

I'm considering grinding a B crank to A specs and using A rods. The Crank is drilled so would need to be plugged and rear slinger cut. I have a 43# flywheel to use with it. Any other considerations?

[Joe K]

I think the usual routine is to have the crank mains ground to some size part way between A size and B size. IIRC, the bolt-to-bolt spacing of the A block does not allow direct insertion of the B crank.

Most go with B rods/rod journals and grind a bit on the rods/nuts/housing to keep it from hitting. Doesn't dropping to A rod size kind of undo the advantage of the B crank?

And the success of modern "slingerless" rear main seal is mixed. Usually requiring re-engineering of the entire rear main block interface. There are kits for this. But like a Cadillac Owner who is quick to buy the best and tell everyone his good fortune/judgment/taste, some are happy and recommend heartily, others still have oil drips on their driveway and say nothing.

And I'm assuming from your lightened flywheel that this is a counterweighted B crank? This part is probably the best recommendation - but there are ways to add weights to an A crank and maybe save some trouble?

Maybe you can tell us more for your rationale?

Thanks,
Joe K

[Crazydaddyo]

If you use Corvair rod bearings as main bearings, you can run the B crank in a A block at 1.800" dia on the mains. That is about the largest you can go with the A main bolt spacing. I have heard that there is a Saturn bearing that is about .025" - .030" larger then the Corvair bearings.

Make sure that the person that grinds your crank doesn't grind a fillet radius on the crank that are smaller then @ .100". The bigger the better.

[jfreddy]

Thanks for the replies. All helpful. I'm limited to using the existing A babbitt, which is at std and in good shape. Also, the rods are new A std. The advantage I see would be having the CWts for less $ than buying a new Burlington.

Any downside?

[Dan McEachern]

If the crank has been drilled straight thru from the rods to the mains and you grind the journals to A size, you may well grind thru to the oil passages in the fillets of the journals before you get the journals to where you want them.

[colin1928]

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Originally Posted by Dan McEachern

If the crank has been drilled straight thru from the rods to the mains and you grind the journals to A size, you may well grind thru to the oil passages in the fillets of the journals before you get the journals to where you want them.

Correct

also you will need to machine the oil slinger not something your normal shop wants to do
or remove it and try a modern style seal

[Joe K]

Originally Posted by jfreddy

Thanks for the replies. All helpful. I'm limited to using the existing A babbitt, which is at std and in good shape. Also, the rods are new A std. The advantage I see would be having the CWts for less $ than buying a new Burlington.

Any downside?

Dan Price has good counterweights. I would go that way and save the drilled countershaft for someone who has/needs a pressure engine.

http://www.dan4banger.com/products.html#javascript:;

There may be others who can add counterweights cheaper than Dan's. I like Dans because they are sweat on and are removable for grinding.

Joe K

[Jim Brierley]

I agree with JoeK.