THE PILOT SAID THE AIRCRAFT HAD JUST LEVELED OFF INTO CRUISE FLIGHT WHEN THE ENGINE SUDDENLY BEGAN TO SPUTTER, RUN ROUGHLY, THEN IT QUIT ALTOGETHER. THE PILOT PERFORMED A FORCED LANDING ON A DIRT ROAD AND COLLIDED WITH TREES AND A BERM DURING THE LANDING ROLL OUT. FAA INSPECTORS EXAMINED THE AIRCRAFT AND FOUND THE ENGINE SEIZED. NO OIL WAS FOUND IN THE ENGINE SUMP. THE OIL SCREEN WAS FULL OF METAL PARTICLES. THE OIL QUICK DRAIN WAS IN THE CLOSED POSITION AND FULLY FUNCTIONAL. NO OIL DEPOSITS WERE FOUND ON THE EXTERIOR OF THE AIRCRAFT AND NO EVIDENCE OF OIL LEAKAGE WAS NOTED TO THE SURROUNDING SOIL. THE LAST INSPECTION OR ENGINE MAINTENANCE OF RECORD WAS ENTERED IN THE LOG BOOKS WITH A DATE OF APRIL 13, 1991. THE PILOT DID NOT HOLD A CURRENT MEDICAL CERTIFICATE. THE LAST MEDICAL CERTIFICATE OF RECORD WAS A THIRD CLASS MEDICAL DATED AUGUST 5, 1985.