Can anyone validate this claim, about valve retainers?
www.racepad.com says this, regarding 1995 M3:
"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."