On June 27, 2019, about 0630 mountain daylight time, a Stinson 108-3, N6116M was substantially damaged when it was involved in an accident near Caldwell, Idaho. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, he was practicing takeoffs and landings in the airport traffic pattern. When the airplane was in the turn between the downwind and base legs with the flaps deployed, the engine ceased developing power. The pilot applied carburetor heat, switched fuel tanks, and attempted to restart the engine but was unsuccessful. He then maneuvered the airplane from base leg to final and the airplane landed hard in a field short of the runway. The airplane struck an airport perimeter fence, nosed over, and came to rest inverted. A review of the photographs furnished by the Federal Aviation Administration (FAA) revealed substantial damage to the fuselage and wings. An on-scene examination of the airplane by the FAA revealed that the flaps were in the up position and the carburetor heat was in the off position. The fuel tanks contained fuel, the engine had a supply of oil, and the air filter was not blocked from the outside. An examination of the engine revealed that the oil dip stick tube and cap had significant amounts of “ferrous and non-ferrous” debris and an automotive remote bypass oil filter system was installed. The inspector added that the pilot conducted his own preventative maintenance. The pilot was not a certificated airframe and powerplant mechanic. According to maintenance records, a certificated airframe and powerplant mechanic reinstalled the engine on March 27, 2019, with a total engine time of 2,500 hours. The mechanic added that the engine had been overhauled by the pilot 25 flight hours before the accident flight. He further remarked that he did not physically supervise the pilot during the overhaul and that the pilot used maintenance manuals to complete the overhaul. The logbook entry for the installation of the overhauled engine stated that the overhaul consisted of the following: - Magnafluxed crankshaft and other internal steel parts - Replaced camshaft, bearings, pistons, rings, valves, seals, and gaskets - Both magnetos were fitted with new points and condensers - Carburetor was fitted with new float and needle - Oil cooler hoses and oil pressure hoses were replaced A cursory postaccident examination of the engine performed by the pilot revealed that “a piston came apart, breaking into small pieces that made their way back into the intake tubes [subsequently] sticking the valves open.” No further information or pictures were provided by the pilot regarding his engine examination. Furthermore, the wreckage and the engine were no longer available for a follow-up examination.