Incident Summary
About half an hour into the flight, while cruising at 8,000 feet MSL, the engine momentarily missed and then resumed normal operation. Shortly thereafter, the engine power decreased to 20 inches of manifold pressure. The pilot informed Air Traffic Control of the situation and requested vectors to the nearest airport, which was 8 miles away. Despite attempts to re-establish engine power, the pilot was unable to restore full performance. The aircraft reached the airport, but the engine lost all power during the final approach. The pilot executed an uneventful forced landing on the runway.
Engine Inspection Findings
Following the incident, an inspection of the engine revealed that the wrong pistons had been installed during an overhaul performed on July 30, 1996. The specified pistons were part number 648044, which correspond to a compression ratio of 7:1. However, the pistons found installed were part number 648045, which have a compression ratio of 8.5:1. This discrepancy likely contributed to the engine power loss.