Lost Frost plugs

I bought the engine as a "crate" unit. It had been built by a trusted individual. I think last year I had it broken in..that is where they attach it to an electric engine and spin it at 1500rpm (i think) for a period of time.

The engine has never had water in it.

I spray painted it last year.

I am completely stumped.

Ian.

There is a clue.... Is there spray paint inside the block and on the surfaces where the missing plugs are?