Big Problems with New 408 +PICS

Does that mean you dont know the end gap? Does your builder? The oil on the heads is typical of a cylinder that has problems. I wouldnt sweat the heads, but again, I totally disassemble them and check seat runout and valve stem clearances. I have seem OOTB seats .010 out of round, but those would seal..Just not very well...lol. If I had to guess, I'd say a combo of things. The honing pattern is odd. But that may just be the pictures too. Take a clearaer pic of a bore with the pistosn down 1/2 way. But I dont think that would cause it to pop a gasket. My money's on the lack of retorque, or surface contamination of the deck or gasket that didnt allow it to bite well. Sealing aluminum and iron together is not easy. Permatorques can do this, but if there was a weaker area because of torquing, it would pop during the pass pumping gasses into the cooling system, and when the throttle was slammed shut, the vaccum level draws coolant into the cylinder. At least it didnt hydraulic and really break something.