This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
I had a catastrophic engine failure taking off in the first flight since a major overhaul of my Continental IO520CB engine. I feathered my left engine, and continued the takeoff, entered right traffic, came around and landed back on the takeoff runway.
I suspect the mechanic/IA who performed the field overhaul failed to properly torque the piston rods to the crank shaft. I have not had the engine disassembled to confirm my theory.
Additionally, I feel the mechanic created this situation by not performing the overhaul in a timely manner. He would work for a few hours, leave the hangar and not get back to the job for days or weeks. This caused him to lose track as to where he was in the overhaul process, and consequently, miss a very important step.
The engine is not repairable, a total loss, but I made it back safely.
Primary Problem: Procedure