[euro911sc]

I don't think that is spalling...

I would be more inclined to say something got loose. If you look at the nut in the first image it looks like an impact mark on the edge nearest the cam loab.

Then the second pic of the valve cover somewhat confirms something may have gotten free or was in there to start. Did you find anything in there rattling around when you took the cover off? Prob. not or you would have mentioned it...

Also, striping the ring gear on a back fire seems a little off as well... must have been one hell of a back fire! Others may have more experience here than I, but if something got stuck and jammed things a bit... well that seems more plausible.

*shrug*

Maybe the culprit is jammed in there where you can not easily see it? Are all the lock nuts there? Valve lock nuts? Tappet Feet?

-Michael