On July 16, 2004, at 0835 central daylight time, a Grumman G-164B, N48675, operated by Custom Air Inc., as an aerial application airplane, was destroyed on impact with terrain and post crash fire during a forced landing. The airplane experienced a total loss of engine power following takeoff from Knox Landing Airport (87NE),York, Nebraska. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 137 aerial application flight was not operating on a flight plan. The commercial pilot sustained serious injuries. The local flight was originating at the time of the accident. The pilot reported to the on-scene Federal Aviation Administration inspector that the accident airplane was refueled along with three other airplanes prior to departing 87NE. The three airplanes were reported to have been fueled with JET A, and the accident airplane was fueled with 100 low lead. The loss of engine power occurred during climb through an estimated altitude of 500 feet above ground level. The pilot stated that he took off for a routine spray flight loaded with fuel and chemical. Approximately two minutes after departure, the aircraft engine developed a total mechanical failure. He stated that he immediately diverted away from traffic on interstate 80 with very little time and impacted a hillside along the interstate. The airframe except for the right outboard wings and horizontal and vertical stabilizers exhibited fire damage. The number six cylinder intake was separated from the cylinder assembly, and the number nine cylinder exhaust was fractured. The Pratt and Whitney R-1340-AN-1, serial number ZP-103477 engine, accumulated an estimated total time since new of 9,030 hours and an estimated time since overhaul of 473 hours. A postaccident disassembly of the engine under the supervision a Federal Aviation Administration maintenance inspector was performed at Covington Aircraft Engines, Inc., Okmulgee, Oklahoma. Results of the disassembly were reported as follows. The number six cylinder intake ear and cylinder were separated from the engine. The intake tube connecting the cylinder's intake port to the engine's blower section was crushed and attached to the cylinder ear and the blower section. The number nine cylinder intake ear was reported to be fractured with the top portion of the ear, including the rocker arm and rocker shaft. The front portion of the ear was melted from the remainder of the ear. The engine oil screen was partially collapsed and no metallic contamination was noted. The carburetor top housing was separated from the lower housing with a hole in the rear portion of the bottom housing. The carburetors mounting flange was distorted and the two rear outside mount flange corners were broken off. These pieces of the mounting flange were attached to the carburetors mount surface on the engine's rear case. The float half in the rear portion of the bottom housing was crushed. The jet sizes per the carburetors assembly parts list was confirmed. No anomalies were noted with the needle valve and seat assembly. The fuel screen did not exhibit a "serviceable" amount of contamination. Bosch magneto, part number SB9RU3, serial number BB24939, exhibited fire damage and rotated with "difficulty." Disassembly of the magneto revealed that the point plate was intact and the phenolic drive gear teeth were intact. The contact finger of the coil was detached from the coil and lodged between the distributor rotor contact collar and the rotor's contact shield. The shield area did not exhibit scoring or impact damage. The area around the coil, adjacent to the contact’s attach point, exhibited a witness of the coil into the charred and discolored insulation material of the coil. Bosch magneto, part number SB9RU3, serial number unknown due to a missing data plate, exhibited fire damage. All of the phenolic components except for the distributor rotor were destroyed by fire. All components of the point plate were intact.