On July 11, 1995, about 1000 central daylight time, a Rockwell International S-2R, N8440V, registered to and operated by M & M Air Service, Inc., crashed shortly after takeoff from a private airstrip near Lambert, Mississippi. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 137 aerial application flight. The airplane was destroyed by a postcrash fire and the commercial-rated pilot sustained minor injuries. The flight originated about 5 minutes before from the operator's private airstrip. The pilot stated that shortly after takeoff during cruise flight, the engine experienced a partial loss of power and smoke was observed near the right side of the engine. He initiated dumping of the chemical and while maneuvering to avoid obstructions, the airplane stalled, impacted the ground then nosed over. A postcrash fire destroyed the airplane. Examination of the engine revealed that the No. 4 cylinder intake valve, rocker arm bosses failed. Review of the engine logbook revealed that the engine was overhauled on May 6, 1994, and had accumulated about 305 hours since overhaul. The total time of the cylinder was not determined.