On May 17, 1998, at 1130 hours Pacific daylight time, a Schweizer G164D, N8177K, was destroyed when it nosed over during a forced landing following a total loss of engine power on takeoff. The commercial pilot was not injured and there was no property damage. At the time of the accident, the flight was departing the Doc Thompson airstrip which is located 9 miles north-northwest of Richvale, California. Visual meteorological conditions prevailed and no flight plan was filed for the 14 CFR Part 137 agricultural application flight. The operator stated in his accident report that, approximately 15 feet agl, he heard a loud "pop" in the engine compartment followed by an immediate loss of engine power. He made a forced landing to a soft dirt field about 800 feet from the end of the runway. During a teardown inspection of the engine, it was noted that four compressor/turbine blades were broken off at the blade/butt interface. The parting surface on the butt side of the break was clean and did not show evidence of progressive failure. It was also noted that the four broken blades were not standard manufacturer's replacement parts.