Pilot Report
The pilot reported that after dropping off a passenger and departing for his home base, he heard a noise while climbing through 5,000 feet. He continued to climb, and the noise seemed to stop, but he noted increasing oil temperature. When he enrichened the mixture, oil pressure suddenly dropped. The pilot turned back toward the departure airport.
Loss of Power
Approximately eight miles from the airport, he heard a knocking noise, followed by a total loss of engine power. Unable to locate the airport, he opted for an off-airport landing on a road. During the landing maneuver, the right wing struck trees, substantially damaging the outboard five feet of the wing structure.
Post-Accident Inspection
Inspection of the engine revealed oil present on the belly of the fuselage from nose to tail. The wing fuel tanks contained about 20 gallons of fuel. The forward crankshaft seal was only partially seated in the engine case nose. The lower number 1 and 4 spark plugs were removed and showed lead fouling. The number 3 and 4 primer lines were found loose at the cylinder. The number 1 and 3 connecting rods failed; the number 2 and 4 connecting rod bearing material was melted and squeezed between the rod cap and crankshaft. The engine case halves exhibited several holes. The number 2 cylinder had cracked the case around the cylinder base and was attached by only two studs.