On September 18, 2004, at 1230 central daylight time, a Cessna 172M, N80237, collided with the terrain and cart wheeled during an off airport forced landing following a loss of engine power near Houstonia, Missouri. The commercial pilot and the sole passenger on board received minor injuries. The airplane was substantially damaged. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The flight originated from the Lee's Summit Municipal Airport (LXT), Lee's Summit, Missouri, at 1200. The intended destination was Columbia, Missouri. The pilot reported that 30 minutes into the flight he heard a "clunk", the engine stopped running, and the propeller was not windmilling. He stated he attempted to restart the engine to no avail. The pilot declared an emergency with air traffic control at Whiteman Air Force Base. The pilot was attempting an off airport landing in a bean field when the right wing struck the ground, the airplane cartwheeled, and a post impact fire ensued. The airplane and engine were inspected by an inspector from the Federal Aviation Administration, Kansas City, Missouri, Flight Standards District Office. The inspector reported the right wing sustained most of the damage. The right main landing gear was separated and the right lower portion of the engine cowling was damaged. The airplane was then destroyed by a post impact fire. Inspection of the engine revealed the piston and piston pin on the number 4 cylinder were separated from the connecting rod. The connecting rod, piston pin, and fragmented piston from the number 4 cylinder; the connecting rod from the number 2 cylinder; and pieces of rod bushing material were sent to the National Transportation Safety Board's Materials Laboratory for examination. The metallurgical examination of the number 4 connecting rod noted the piston pin end of the rod was fractured and the fractured ends were deformed inward. According to the Materials Laboratory Factual Report the fractured surface revealed, "a thumbnail region typical of a fatigue crack that emanated at the forging parting plane on the exterior surface... . The fatigue origin areas contained ratchet marks indicating that fatigue cracking initiated at multiple sites. ... The fatigue crack extended through approximately 60% of the wall thickness... ." The remaining components that were submitted for examination either contained mechanical impact damage or overstress signatures. The engine, a Lycoming O-320-E2D, serial number L-30540-27A, was overhauled on August 11, 2003, at an engine total time of 3,918.7 hours. The engine had accumulated approximately 70 hours since the overhaul. Maintenance records indicate the connecting rods were magnafluxed, rebushed, checked for alignment, and reinstalled in the engine during the overhaul. The connecting rods were the original engine rods.