Two things jump to mind.

Jumped timing chain punching a valve through the piston top or a serious case of pinging.

How do the valves look and what octane did you normally run?

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.