Incident Summary
The pilot reported that during flight, the engine began to run rough. He diverted towards a nearby airstrip, but while en route, a "bang" occurred and smoke began entering the cabin. At that point, he shut off the fuel, magnetos, and master switch, then lost about 1000 to 1200 feet while clearing the smoke. He was committed to land downhill on the strip. During touchdown on the rough strip at about 90 mph, the nose gear failed. Subsequently, the aircraft nosed over.
Investigation Findings
An investigation revealed that a connecting rod had failed. The engine had exceeded the manufacturer's recommended time-between-overhaul (TBO) by about 215 hours. Reported findings indicated the engine bore evidence of a high amount of wear on most moving parts. The temperature and elevation at the site were about 75 degrees Fahrenheit and 3960 feet, respectively.