On May 10, 2006, at 1815 eastern daylight time, a Piper PA-28-180, N15702, registered to a private owner, operating as a 14 CFR Part 91 personal flight, experienced a loss of engine power while descending in the vicinity of Hemmingway, South Carolina. Visual meteorological conditions prevailed and an instrument flight plan was filed. The airplane received substantial damage. The private pilot reported minor injuries. The flight originated from Columbia, South Carolina, on May 10, 2006, at 1720. The pilot stated he was cleared by Myrtle Beach Approach Control to descend from 7,000 feet to 3,000 feet. While descending through 6,000 feet, the pilot heard a "pop" sound, and the engine began to run rough with partial power. The pilot looked at the engine monitor gage and the No. 3 engine cylinder temperature gage indicated 900-degrees. The pilot immediately programmed his global positioning system for the nearest airport. The pilot declared an emergency with Myrtle Beach Approach Control, decreased power, and requested clearance direct to Hemmingway Stuckey Airport. The controller approved the request and the pilot made a 180 degree turn and continued his descent through the clouds. Upon reaching visual flight conditions the pilot observed the airport straight ahead. The pilot descended over the airport to lose altitude and turned on final approach. The engine quit at 300 feet, and he realized he could not make it to the airport. He observed an open field to his left and initiated a forced landing. The airplane collided with trees and the ground and the pilot exited the airplane. Examination of the engine assembly revealed both exhaust stacks and the oil filter was bent. The oil dip stick was removed and the oil level indicated 5 quarts of oil. The oil filter was removed, cut open, and no foreign object damage was noted. The air filter was examined and no anomalies were noted. Examination of the carburetor air box and door, carburetor inlet, throat and venturi revealed no anomalies. All spark plug leads were removed and no anomalies were noted. All bottom spark plugs were removed. The No. 3 bottom spark plug electrode was bent and the No. 3 top spark plug was damaged. The No. 3 cylinder was removed from the engine and examined. The cylinder walls, piston skirt and rings, push rods, rocker shafts, and valve springs revealed no anomalies. The internal surface of the No. 3 cylinder head and piston face had numerous indentations. The valves were removed and examined. A portion of the face of the No. 3 exhaust valve was missing. A compression check was conducted and compression was normal on cylinders No.1 and No. 4. Compression on the No. 2 cylinder was weak. Examination of the No. 2 cylinder spark plugs revealed the center electrode ceramic insulators were broken and missing. A visual inspection through the No. 2 lower sparkplug hole revealed a foreign object embedded in the No. 2 cylinder head. The No. 2 cylinder was removed and a piece of the No. 3 exhaust valve was embedded in the No. 2 cylinder head. The embedded piece was removed from the No. 2 cylinder head, cleaned and matched the portion of the face of the No. 3 cylinder exhaust valve. Pieces from the No. 3 exhaust valve were forwarded to the NTSB Material Laboratory for further examination. Examination of the No. 3 exhaust valve revealed the valve failed due to fatigue emanating radially inward due to thermal overstress. The pieces of the No. 3 exhaust valve were returned to the registered owner on October 13, 2006, by the NTSB Materials Laboratory.