What happened
The pilot reported that shortly after leveling off at 11,500 feet mean sea level, the aircraft's engine experienced a catastrophic failure. The explosion resulted in both windshields becoming covered with oil and fire. The fire extinguished itself during the subsequent emergency descent. The aircraft successfully landed on runway 30 at Bishop Airport in Bishop, California, without further incident.
The investigation
A disassembly examination of the engine revealed that the crankshaft had failed at the short cheek between the number 3 main journal and the number 4 crankpin. Both the number 3 and number 4 connecting rods, along with the camshaft, were fractured. Inspection of the pistons showed no evidence of detonation.
Examination of the backside of the connecting rods, main journal bearings, and both halves of the crankcase revealed extensive fretting signatures. These signs indicated that misalignment occurred during the manufacturing process. Metallurgical examination confirmed that the crankshaft failed due to fatigue. All other fractures were determined to be overload failures subsequent to the initial crankshaft failure. The engine had accumulated 602 flight hours since new.
Findings
The primary contributing factor was crankshaft fatigue resulting from manufacturing misalignment. This defect led to the catastrophic engine failure and subsequent structural damage to connected components.