On May 16, 1998, about 1340 eastern daylight time, a Nanchang CJ-6A, N158T, registered to a private individual, experienced a loss of engine power and collided with terrain during an attempted forced landing in a field about 1.5 miles east of Pageland, South Carolina. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 personal flight. The airplane was substantially damaged and the private-rated pilot, the sole occupant, was seriously injured. The flight originated about 10 minutes earlier from the Cheraw Municipal Airport, Cheraw, South Carolina. The pilot stated that while flying at 800 feet agl, he felt a vibration and observed an object protruding from the engine cowling, and a resulting loss of engine power. While attempting to clear trees with the landing gear and the speed brake extended, the airplane stalled, impacted the ground nose low, then nosed over and came to rest inverted. The pilot was not wearing the installed shoulder harness. Examination of the engine by the FAA inspector revealed that the No. 9 cylinder was separated from the engine and the auxiliary rod piston pin hole was elongated. The auxiliary rod sleeve was not in place. Nonferrous metal was noted inside the engine case. Review of the maintenance records revealed that at the time of failure, the engine had accumulated about 425 hours since new.