Hey Folks,
I'm swapping to a 20R head, new header, exhaust, cam, blah blah. While fitting my header and exhaust, I sat my old head onto the block. I noticed that the head will rock left and right... tapped it with mallet to make sure dowels were seated... no change. So then I tried my newly milled 20R head, but the result was the same. The block and both heads seem to check out straight with a straight-edge (the pistons are preventing a complete block check, but what I can check appears flat. Still with no head gasket, I put my old head back on bolts into the old head and torqued (in the proper sequence) to 5-10 ft lbs. The head seemed to pull down fine, but when I loosened the bolts it came back up some...
This motor is in a toy RV, and the last thing I want is to blow a head gasket 300 miles from home next week. This is my first time into this engine.

BTW, this block is an 82 (dual row TC) , 20r head is late 70s...unsure of year.

Anyone had any similar experiences?