This was at http://www.racepad.com/ on the E36 M3 1995 page. Does anyone have any stories about this?
Early production (pre 10/95) versions used softer valve retainers. These should be checked around 50K miles. BMW underestimated the wear on these and the softer metal is prone to wear. A worn valve retainer will result in catastrophic engine failure. The valve will drop through into the cylinder and whack the piston to bits and bend the valve stems.