This is what killed my '54 235. The front main cap was cracked on mine, a vertical crack running down the outside of the bolt hole. My crack runs from below the bolt head down to the cap parting line. Since the closest line-bore shop is in Georgia, my engine is junk.
Listen to the voice of experience: If you find a cracked main cap, your motor is junk. Doing anything but tossing that block in the closest smelter is pure folly.
I know you're in the middle of changing something or other, but a cracked cap is a TKO. You're wasting your time. How do you think I felt after installing 300 dollars worth of clutches, gaskets, tranny bearings, etc just to find out my motor was junk???
Bring the cap to a machinist or post pics here to verify that it IS cracked.
Alternatives? If you're easy on the engine, it may last for awhile.
So find another engine, and run this one 'till it flies apart.
I think this is caused by vibration and metal fatigue. The youngest 235 was built 40 years ago, and the cast iron in these engines is starting to crystalize and fail. The place where this failure will show up first is around the main cap bolt holes.
Chip
