I'm on the verge of purchasing a cheap SBC Vortec truck engine locally. It's partially stripped (intake and 1 head off) and was removed from the Suburban it was in because one of the heads lost an exhaust seat which ended-up putting a few dings in the piston and the chamber. Also, the same head has a MONUMENTAL crack in it going from one of the bolt holes across the sealing surface of the head. Anyway, the guy has a pair of good L98 iron heads which he's supplying with the engine. My question is this... if the head lost that valve seat due to a severe overheat, it's possible that the block cracked at the same time. Does that sound reasonable? If so, is it essential to magnaflux or pressure-test the block at a machine shop, or are cracks usually visible to the naked eye and a good flash light? I'm taking a bit of a gamble on the engine given what happened to it, but the cylinder bores look good and, being a Vortec, it's a factory roller block.