My grandfather rebuilt a 235 many years ago because the block was cracked. I don't remember the name of the test (magnaflux maybe?) that they ran to determine that it was cracked, as I was a young lad at the time, but he seemed certain. He got another block from a junkyard that was supposed to be good. After he finished rebuilding it and took it out on its maiden voyage, he got about 1 mile before the engine started acting up. He drove it back home, and pulled the engine again. Dismantled the engine and had the new old block tested. More hairline fractures. This time he had the replacement block from the junk yard checked before he rebuilt the engine. No problems with the block and none with the rebuilt engine when he got done. So, that's two cracked 235 blocks that I have personal knowledge of. Anything old can break after years of heating and cooling cycles.
