On June 19, 2003, about 1145 central daylight time, an Allied Ag Cat Productions, Inc. G-164B, N8375K, piloted by a commercial pilot, sustained substantial damage when it nosed over during a forced landing following an in-flight loss of engine power near Dyess, Arkansas. The aerial application flight was operating under 14 CFR Part 137. Visual meteorological conditions prevailed at the time of the accident. No flight plan was on file. The pilot reported no injuries. The local flight departed from Marked Tree Municipal Airport, near Marked Tree, Arkansas, at 1120, and was maneuvering to view a field when the flight sustained the loss of engine power. The pilot stated: Finished field and flew 2 miles northeast to look at next field. Looked at field - flew up to apprx 500 ft [altitude] to head back towards Marked Tree. Leveled off at 500 ft - looked back to left to make sure it was clear to turn, looked back to check gauges, felt like someone reached over [and] pulled power off airplane. Looked at temperature guage - guage showed 700 [degrees]. But felt loss of power. Knew airplane was loosing power and speed. Set up for emergency landing procedures. Seen turn road - thought I could land in turn road - prop quit turning - landed on road - run out of road (headed east) - jumped ditch to miss dug up culbert - landed in rice field (watered and gumbo mud.) Airplane flipped over on back. A Federal Aviation Administration Inspector arranged a tear down inspection of the engine at a certified repair station. Excerpts from the repair station's report stated: 2.3 The technician disassembling the "PY" line from the fuel control unit noted that the line fitting at the fuel control unit was not tight, even though it was safetied. It was not necessary to use a wrench to detach the line from the fuel control unit. The "P3" fitting installed in the fuel control unit on the side opposite the PY line could easily be moved by hand. Both fittings were safety wired when the engine was received. ... 2.6 The compressor bleed off valve, part number 3100829-03, serial number: A-3843 was removed and two of the part number MS9923-31 attach screws were observed to be loose (left side, pilot view). Marginal torque was required to remove the two right side screws. The valve was lifted from the gas generator case and what appeared to be a piece of the O-ring packing required for installation between the bleed off valve and the gas generator case was found resting in the threaded hole vacated by the left rear attach screw (photo page 7 of 8). A patch of black colored, flexible material was found lightly adhering to the area adjacent to the recess in the flange of the bleed off valve normally accommodating the sealing O-ring packing (photo page 8 of 8). Portions of the bleed off valve / gas generator mating surface exhibits black colored deposits in an outward radiating pattern. The bleed off valve, the patch of black, flexible material and the approximately 1/8 inch section of O-ring packing was retained for further evaluation. 2.7 The remainder of the engine was disassembled for inspection and no other potential cause for the reported loss of power were discovered. ... The repair station's engine investigation report is contained in the public docket of this accident report.