340 Hydraulic lock inspection update...
Found water in #7 cylinder after pulling all plugs. No water in oil. When I add water to radiator, it flows out plug hole! Pulled intake and valve covers to find valve spring broken off and push rod bent. Removed rocker shaft. Actual valve stem is loose but won't pull completely out. Looking into head passage from lifter valley, I can see head casting is broken/cracked inside around threads... see pic.