On August 9, 1996, at 0800 central daylight time, a Piper PA-28-180, N2559R, registered to and operated by a private owner as a Title 14 CFR Part 91 flight, sustained substantial damage during the forced landing following a loss of engine power near Midlothian, Texas. The private pilot was not injured and the passenger received minor injuries. Visual meteorological conditions prevailed for the planned personal cross country flight to Angel Fire, New Mexico. A flight plan was not filed. The accident occurred at the flight origination airport. During telephone interviews, conducted by the investigator-in-charge, the pilot reported that about 1/4 mile north of the departure end of runway 35 and 200 feet AGL, an engine vibration and a partial loss of power occurred. During a 180 degree turn toward the airport the airplane lost altitude and the landing was made to a soft field. Structural damage occurred to the landing gear, propeller, firewall, engine mounts, and the left wing. The pilot stated that the engine had 170 hours since the overhaul. The pilot further stated that prior to this accident "there had not been any previous indications of engine problems since the engine overhaul." In October 1996, the airplane was examined under the oversight of the FAA inspectors. During an engine test run at full power, the inspectors observed an engine power drop of 200 RPM; however, they were not able to duplicate the engine vibrations that had been reported by the pilot. During an examination of the magnetos, the magneto timing was found to be 27 degrees before top dead center (BTDC). According to the FAA inspector, 25 degrees is the normal timing for these magnetos. The carbon brush was missing from the right magneto. Further inspection revealed that the rocker arms had been installed in reverse positions on all four cylinders. One FAA inspector stated that "the exhaust valve was not receiving adequate lubrication." The other FAA inspector stated that "an indication of inadequate lubrication on the exhaust valve would be excessive and premature wear in the valve guides, which in turn results in valve sticking and excessive and severe vibration of the engine." An FAA certificated mechanic, who examined the engine, stated that the "wear patterns on the exhaust valve rotator caps indicated that the exhaust valves had been binding." A review of the maintenance records by the FAA inspectors and the investigator-in-charge revealed that the airplane was returned to service on December 4, 1994, following a major engine overhaul. Overhauled magnetos were installed at the time of the engine overhaul. On January 21, 1996, the airplane was returned to service following a 100 hour inspection at which time the mechanic entry stated in part: "checked mag[neto] timing to eng[ine], ops ck [operation check] good."