On August 1, 2013, about 0945 Pacific daylight time, a Weber GPA-2 (Long-EZ) experimental amateur-built airplane, N199BW, was substantially damaged during a forced landing following a loss of engine power near Brentwood, California. The airline transport pilot, the sole occupant, received minor injuries. The pilot was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the cross-country flight, which had originated from Livermore Municipal Airport, Livermore, California, approximately 30 minutes before the accident. A flight plan had not been filed. The pilot stated that he was at an altitude of 4,500 feet when he noticed a slight vibration in the airplane. He examined the instrument panel and saw that the engine's cylinder head temperatures were rising above 450 degrees Fahrenheit. He did not remember looking at oil temperature or pressure indications. He diverted toward the nearest airport, but the engine lost power. He selected a road for a forced landing, but during the approach to the road he saw power lines ahead, so he attempted to make a 180-degree turn and land in the opposite direction on the road. He was unable to complete the turn, and he landed in a corn field. Both wings sustained substantial damage. A Federal Aviation Administration (FAA) inspector examined the airplane at the accident site the day after the accident. He reported that the engine was still in place in the rear of the fuselage, and it was upright and appeared to be level. He checked the engine's oil level and found that it was full, and the oil appeared to be very clean. The airplane was then retrieved to a secure salvage yard. The inspector again examined the airplane on August 9, 2013. He found the engine still mounted to the airframe, and he was able to rotate it by hand. When he attempted an engine start, the engine immediately started. He moved the throttle back and forth, and the engine accelerated smoothly and without hesitation. Following the engine run, the inspector removed and split the oil filter. It was clean with no metal debris. The inspector also removed the carburetor's fuel screen/filter, and it was clean. The examination and test run revealed no evidence of any pre-impact discrepancies with the engine that would have prevented normal operation.