Hi Jerry,
Since your cylinders shouldn't be cracked to allow coolant to enter, I would suspect head or gasket (the only other choices).
Since you said the gasket looked good, I'm thinking head.
If you can't see a crack in it, take it to have it magnafluxed.
I'm betting there's a crack.
Worst case scenario, another head purchase to be made. It could be worse.
Good luck!
