[tekuhn]

Any possibility you forgot to torque the #4 main cap? With the visible gap between the cap and block it seems like you would have heard something if it broke enough to have that much gap with it fully torqued. That or perhaps the cap hung on the alignment stud or something was trapped underneath? All just guesses, of course. Sure sounds like you did everything right and it's certainly a high quality build overall. It sure sounds like you knew what you were doing. I hope the mystery gets solved. I think you'll regret selling the car down the road, so don't rush into that decision. Hang in there...