On July 5, 2000, about 0820 mountain standard time, a Cessna 205, N8154Z, collided with a sign during a forced landing on a road near Tacna, Arizona. A total loss of engine power precipitated the forced landing. The commercial pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The pilot and his wife were not injured; the airplane sustained substantial damage. The personal flight departed Yuma, Arizona, about 0800 en route to Sedona, Arizona. Visual meteorological conditions prevailed and no flight plan had been filed. Initially reported as an incident, a Federal Aviation Administration (FAA) inspector upgraded it to an accident on July 11, 2000, after a visual inspection of the damage. The pilot reported that the airplane was in cruise flight when he heard a loud noise in the engine compartment and felt a severe vibration. The engine immediately lost power, and he set up for an emergency landing on a gravel road. He made a full flap landing on the road, but struck a road sign, crushing the right wing leading edge back to the spar. Upon initial inspection, the FAA accident coordinator noted that the engine case fractured in the vicinity of the No. 6 cylinder, and the cylinder's base was displaced away from the case. He said the engine could not be rotated by hand, but oil was in the oil pan. Sun Western Flyers in Yuma tore down the engine under the supervision of the accident coordinator. The coordinator summarized the results of the inspection. He observed an adequate oil supply in the engine, and did not observe any discoloration of the engine components or other signs of oil starvation. He did not observe mechanical damage on the piston face that indicated the possibility of a stuck valve. The coordinator reported that the piston in cylinder No. 1 fractured at the piston pin. The piston rod continued to rotate, which fractured the camshaft in half and separated both magnetos. The piston rings in cylinder No. 1 fractured and scored the interior wall of the cylinder in the direction of the cylinder stroke. After reviewing the airplane's logbooks, the accident coordinator noted that the airplane received an annual inspection 1 month prior to the accident, and all airworthiness directives and required inspections had been complied with. He said the manufacturer recommends that this engine model should be overhauled at 1,500 hours; however, this engine had over 1,820 hours since overhaul.