As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN THE NR 4 CYLINDER WAS REMOVED, THE EXHAUST VALVE HEAD WAS FOUND TO BE BROKEN OFF, ABOUT .5 INCH FROM THE FACE OF THE VALVE, CAUSING FAILURE OF THE PISTON AND FAILURE OF THE INTAKE VALVE. THE CIRCUMSTANCES OF THE FAILURE CAUSED A LOSS OF ENGINE POWER AND A FORCED LANDING IN A FIELD. THE PILOT WAS UNHARMED. (K)