On April 4, 1994, at 1749 hours Pacific daylight time, a North American P-51D, N1451D, was substantially damaged during a forced landing at Chino, California. The forced landing was precipitated by a loss of engine power. Visual meteorological conditions prevailed for the personal cross-country flight and no flight plan was filed. The pilot and passenger received minor injuries. The flight originated at Chino at 1745 hours as a local test flight with a planned continuation to Prescott, Arizona. This was the first flight since completion of a major rebuild and restoration. The pilot planned to circle the airport area several times to check the operation of the aircraft prior to departing for Prescott. Ground witnesses stated that they do not recall seeing the airplane go through normal ground power checks prior to flight. While maneuvering in the airport area, the pilot reported that he experienced an oil mist in the cockpit. The pilot declared an emergency and the Chino Air Traffic Control Tower cleared the aircraft to land on runway 21. The aircraft collided with terrain in a cow pasture about 1/4 mile north of the airport. During the postcrash examination of the engine and the oil system, it was observed that the inlet and outlet oil lines to the oil cooler had been inadvertently crossed. An aluminum beaded oil line with a rubber hose and clamp was found disconnected from the cooler on the inlet side. According to a mechanic familiar with the aircraft and engine types, the crossing of these oil lines will cause a pressure build up and can force the hose to uncouple. Examination of the airplane fuselage revealed a trail of engine oil from the oil cooler aft along the belly to the tail. PERSONNEL INFORMATION Review of the Federal Aviation Administration (FAA) airman record and medical files revealed that the pilot's last flight physical of record was dated March 23, 1981. At the time of that examination, he reported a total flight time of 8,000 hours with 200 in the last 6 months. AIRCRAFT INFORMATION According to the airframe logbook, the last documented aircraft maintenance was performed on April 12, 1987, at a total airframe time of 1,751.3 hours. According to an engine logbook, the engine installed at the time of the accident had been overhauled on May 3, 1983, and had accrued 456.3 hours of operation. The last documented annual inspection was dated April 12, 1987. The airplane was being rebuilt at Chino after a previous accident. The work had been in progress for several years. No inspection, repair, or overhaul data was recovered regarding the restoration or rebuilding of the airplane.