On January 4, 2003, about 0800 Pacific standard time, an amateur built experimental Farmer R B, Davis DA5-A, N7053U, experienced a loss of engine power during cruise flight and collided with a berm during a forced landing near Apple Valley, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, was seriously injured; the airplane sustained substantial damage. Visual meteorological conditions prevailed, and a flight plan had not been filed. The personal cross-country flight departed Apple Valley about 0745, with a planned destination of Yucca Valley Airport, Yucca Valley, California. In a written statement, the pilot reported that about 10 minutes after departing Apple Valley, with the airplane cruising about 1,000 feet above ground level (agl), the engine started running roughly. In an effort to smooth out the engine, he manipulated the carburetor heat control to the "on" position and enriched the mixture. Despite his efforts, the engine continued to run roughly and the rpm began to drop, with the propeller eventually coming to a stop. He selected a paved highway to touchdown upon, but decided the automotive traffic was too heavy and opted to land next to the highway in open desert. During the landing roll out the nose wheel impacted a berm and the airplane nosed over, coming to rest inverted. The pilot further stated that he examined the airplane after the accident occurred. While examining the Continental C-85 engine, he found that the number 1 and 3 cylinders showed evidence of detonation. He noted that the pistons were swollen, which he thought was a result of excessive heat from the detonation.