On October 13, 2003, at 1028 central daylight time, an amateur-built RV-7A, N707DD, piloted by an airline transport pilot, was substantially damaged during a forced landing following a complete loss of engine power while in cruise flight near Augusta, Missouri. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The pilot, who was the only occupant, received minor injuries. The local flight originated from the Spirit of St. Louis Airport, St. Louis, Missouri, about 1015. The pilot reported that while cruising at 1,000 feet above ground level the airplane's engine suddenly quit. He reported that attempts to restart the engine were unsuccessful and he executed a forced landing to a dirt road between two farm fields. The pilot reported that during the landing the nose landing gear dug into the soft sandy ground and the airplane susequently nosed over. The airplane was powered by a Subaru automobile engine that had been converted for aircraft use. The engine induction system included a belt driven supercharger. A Federal Aviation Administration Inspector conducted a postaccident examination of the airplane. The examination revealed that the supercharger drive belt and the alternator drive belt were broken. A hole was found in the plastic timing-belt cover. Pieces of the alternator belt were found within the remaining portion of the timing-belt cover. Further examination revealed that the intake and exhaust valves had struck the piston tops.