https://grassrootsmotorsports.com/forum ... 824/page1/

I got stuck into this thread and found it quite interesting. The gentleman bought an R63 AMG and the head bolt snapped off warranty, which caused damage to the engine. MB quoted him 57K for a new engine, so he is going the personal route and rebuilding it himself. It's a long read (80+ pages), but following the progression is neat. Apparently the head bolts up to a certain timeframe on this engine are a weak point, the head bolt top snaps and shatters the bolt.