On July 2, 2003, at 1008 central daylight time, a Piper PA-24, N6315P, piloted by an airline transport pilot, sustained substantial damage during a forced landing following an in-flight loss of engine power near Winamac, Indiana. Visual meteorological conditions prevailed at the time of the accident. The pilot and his four passengers reported no injuries. The 14 CFR Part 91 personal flight was operating on an IFR flight plan. The flight departed from Plymouth, Michigan, at 0819, with an intended destination of Perryville, Missouri. The airplane's engine stopped producing power during cruise flight. The pilot was given radar vectors to the Arens Field Airport (RWN), Winamac, Indiana. The pilot was not able to reach RWN and executed a forced landing in a rough plowed field. A postaccident examination was conducted by the Federal Aviation Administration. During the initial examination of the airplane's engine, valve train continuity could not be established. Rotation of the crankshaft produced no movement of the valve train components. A subsequent examination of the accessory section of the engine revealed that the crankshaft gear retaining bolt was missing and the gear's anti-rotation pin was sheared. The oil pan of the engine was examined and no bolt was found. The crankshaft gear retaining bolt was not found within the engine. A review of the maintenance records revealed that the engine was last overhauled on April 6, 1986, and had accumulated 522 hours time in service since the overhaul. No subsequent logbook entries were noted that indicated removal of the crankshaft gear or retaining bolt.