Checking Head and cylinder for warp.

how can I check head and top of cylinder to see if they are warped? Funds are tight would like to get some kind of idea as to what needs to go to machine shop.Engine was in BIG rain storm for 40 miles now leaking oil where head and cylinder meet. Took water in thru backing plate, believe engine may have tried to compress water

[Pa]

Machine blue the surfaces and rub them lightly against a very fine emery cloth taped tightly to a very flat sheet of heavy glass panel. The high spots of bluing will rub off right away and indicate just how warped the surfaces really are.

A dail indicator will do the trick.