The only ways I know of to crack a block are serious overheating or freezing.

If you did neither of those it's extremely unlikely, IMO, that the block is
cracked.

Check the easy stuff first. Risers? Manifolds? Gaskets for same? Head
gaskets? Heads? Block face? Compression test can help determine the
likelyhood of a failed head gasket.

For heads and block face use dye penetrant and developer. With heads pay
particular attention to areas around valve seats.

My best guess.... a gasket.

Good luck.

Butch