You've checked the torque on the bolts correct?
I guess a small hole in a piston or a stuck ring could manifest it's self in this way but If you had a hole in a piston or internal damage you would see enough blow by to know somthing was up!

 

Well I got the head pulled and #1 cylinder has pretty good score marks that you can feel all around cylinder wall, #5 and #6 also have a fe marks in them. Not sure what caused it, maybe piston expanding or lack of oil? And I'm still not completely sure where the noise was coming from. But iguess I'll go ahead and pull the engine and tear into further.