Inliners International Forums General Discussion Engines 261 engine - cracked front crank end cap

Ok a couple of things to go over here for clarity.

First is that the main bearings on stovebolts were never poured babbit. From the original design in '29 the mains were insert type bearings - but they were made to an imprecise oversize that allowed them to be line bored to whatever spec the crank was ground to: STD or undersize. In '47 the precision type bearing was introduced and used in the factory on all '48 models - and the repair parts were stocked at the Parts Counters for use back to '37 (when the 216 was introduced). This saved labor in the factory and the repair bays.

As for the bearing caps you've scored I am afraid I have bad news. That set is from '54 - Casting numbers as follows: Front - 3701245, Front inter 3701246, Rear Inter 3701247, Rear - not cataloged:

The '54 and early '55 (first series) are the last to use dowel/staked bearings. In the second series design the block and the cap have a tang machined into them and the back of bearing shells mate with these tangs to keep them from spinning in the journal.

Some will suggest that it is best to change caps as a set and then to have the alignment checked/tweaked to make sure everything is on center. Chevy Parts Master catalogs don't say anything about sets of caps - and they aren't cataloged that way. If replacing just one cap - again the alignment should be checked by a machinist to be sure.

I don't know if you can improvise that front cap onto a newer style block. But it certainly wouldn't hurt to fit it to your block and see what is different in terms of the way the bearings fit and are retained.

Internet searches are also helpful in terms of tapping into the experience of others.