The engine is out.
The Carnage:
Some Disassembly Acquired
It took a big bite out of the head along with nibbles here and there.
The lifter hiding in shame
I'm blaming this guy, and you'll see why later. There was scarring along the side of the lifter, but I can't be sure if it was the cause or result of the failure.
The home of the lifter
It's difficult to see, but there is damage around the lip of the hole.
Dun-dun-DAA! The Rocker
Note the pin, while starting to walk, is still in place. The roller spins freely too.
I have two theories.
1. The lifter failed somehow. Either it somehow wasn't supplied oil (there are no other signs of oil starvation in the head) or it somehow bound up in its seat. This let it retract into the head far enough to let the rocker come free.
2. The walking pin in the rocker allowed the roller to bind up and overheat, locking the roller. But the roller isn't discolored like it would be if it overheated, and the cam doesn't show signs of that it was grinding against a stuck roller.
I'm leaning towards #1, a lifter failure of some sort, as the cause.
The question now becomes. How do we prevent this from happening again? And is it worth doing, or would it be more practical to just get a replacement head and hope it doesn't happen again? I love this car, and the last weekend I had it it was brilliant. But I wonder if an outside observer would think it unwise to stick with this car...