On December 9, 2006, at 1430 central standard time, a Cessna 140, N76379, owned and piloted by a private pilot, received substantial damage on impact with terrain during a forced landing on a farm field near Vienna, Missouri. The pilot stated that the engine lost power after he heard a "bang." Visual meteorological conditions prevailed at the time of the accident. The pilot reported no injuries. The flight last departed from Rolla National Airport (VIH) Rolla/Vichy, Missouri, at 1410. The pilot purchased the airplane and had taken delivery of it at VIH on the day of the accident. The airplane was powered by a Continental C-85-12F engine, serial number 25578-6-12, which according to logbook entries, was last overhauled on July 25, 1990, and accumulated a total time since overhaul of 257.5 hours. A disassembly examination of the engine at Teledyne Continental Motors, Mobile, Alabama, revealed three of the crankshaft cluster gear bolts were fractured through. The bolt fracture surface features were consistent with fatigue. Additionally, the crankshaft gear had a hole where a crankshaft dowel was later installed following a design change in 1948 and was reflected in subsequent maintenance manuals. The dowel is used as a reference in machining the crankshaft. During the disassembly, the tappets fell out when the engine was overturned during the disassembly. It was later noted that the tappets did not contain retaining hardware. The interior of the crankcase halves contained a black colored residue when the oil was drained. Teledyne Continental Service Information Letter, SIL98-9A, Time Between Overhaul Periods, states that engines are to be overhauled at least every twelve years.