On July 31, 1997, at 0814 hours mountain standard time, a Piper PA-28R-180, N4667J, collided with a dirt berm in a cotton field and nosed over following a forced landing near Buckeye, Arizona. The forced landing was precipitated by a total loss of engine power while the aircraft was climbing to a cruise altitude. The airplane sustained substantial damage. The private pilot who was in the left seat, and the owner, who was also a private pilot and in the right seat, sustained minor injuries. The airplane was operated as a personal flight under 14 CFR Part 91 when the accident occurred. The flight originated in Buckeye, and visual meteorological conditions prevailed at the time of the accident. The owner of the airplane holds an FAA Airframe and Powerplant mechanic certificate, and performs the maintenance on the aircraft. Review of the maintenance records and an interview with the owner revealed that he had complied with AD 95-26-13, which required the replacement of the oil cooler hoses. This maintenance was performed on July 25, 1997. The owner said he replaced two oil cooler lines, then subsequently ran up the engine to idle, but did not remove the engine cowling to check for signs of an oil leak. According to Lycoming, the reported idle run/leak check was "most likely of a duration not sufficient to produce enough heat to activate the oil cooler by-pass valve, thus diverting the engine oil around the oil cooler. It is unlikely that a leak would have been detected until the engine obtained normal operating temperature." The airport manager noticed a large amount of oil from where the airplane was run up leading out to the runway for quite some distance. The engine was torn down on August 7, 1997, at Air Transport, Phoenix, Arizona under the supervision of the Safety Board and a complete report of the examination is appended to this report. No lubricating oil was found within the engine. The engine was seized and the crankshaft would not rotate. Heat distress was observed to the internal bearings and journals, with the number 2 connecting rod separated from the crankshaft. The remaining engine rotating group components and valve train were examined further with no evidence of any other mechanical malfunction observed. The Lycoming engine representative noted that the "B" nut of the oil cooler line that attaches to the engine accessory case above the left magneto was loose and required an 180-degree turn to tighten. The owner of the aircraft said that as the aircraft was descending he had to manually hold the emergency landing gear extension lever in the "override" position in order to keep the landing gear from extending. He told investigators that as the aircraft was about to land in the cotton field, he "let go of the lever in order to brace himself." The landing gear immediately extended. As the aircraft touched down in the field, it nosed over onto its back. According to the Piper Aircraft Corporation representative on scene, the examination of the accident airplane revealed that the emergency landing gear override system had no lockout mechanism installed. On October 19, 1983, Piper Aircraft issued Service Bulletin No. 769 which recommended that aircraft equipped with back-up landing gear extension systems install a lockout mechanism. On March 4, 1988, Piper Aircraft issued Service Bulletin No. 866A allowing operators of aircraft equipped with back-up landing gear extension systems to either remove the system or review and understand all the information contained in the applicable airplane Flight Manual/Pilot's Operating Handbook pertaining to the normal and emergency operation of the system. Service Bulletin No. 866A requires aircraft affected by Service Bulletin No. 769 to comply with that bulletin prior to or concurrent with compliance with Service Bulletin No. 866A. Piper Aircraft considers compliance with Service Bulletin No. 866A mandatory.