On February 17, 2004, at 1433 Pacific standard time, a Grumman-Schweizer, G-164B, N6774K, nosed over during the landing flare/touchdown about 8 miles north of Tracy, California. The airplane was substantially damaged during the impact sequence and was subsequently destroyed by a post impact ground fire. The airline transport pilot was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed. Trinkle Ag Flying, Inc., Tracy, operated the airplane under the provisions of 14 CFR Part 137. The agricultural flight originated from a nearby field about 1400. The pilot indicated to the National Transportation Safety Board investigator that while cruising between airstrips, the engine began to "flutter," and he experienced a loss of engine power. Unable to sustain flight, the pilot made a forced landing on a nearby dirt airstrip. Approaching the airstrip, the airplane's landing gear impacted a dirt berm. Thereafter, the airplane nosed over in the adjacent muddy field. The airplane was equipped with a Pratt & Whitney, R-1340 engine, which was manufactured in the 1940's. It had been operated for about 709 hours since receiving its last overhaul. The airplane's total airframe time was 11,773 hours. The event that precipitated the loss of engine power was not ascertained.