On March 30, 1998, about 1420 Alaska standard time, a wheel equipped Piper J5-C airplane, N4769C, sustained substantial damage during a forced landing, about 2 miles southeast of Valdez, Alaska. The airplane was being operated as a visual flight rules (VFR) local area personal flight when the accident occurred. The airplane was owned and operated by the pilot. The certificated commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed. The flight originated at the Valdez Airport, about 1415. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on March 31, 1998, at 1055, the pilot, who is an aviation mechanic, reported he recently completed an engine overhaul on the accident airplane. The accident flight was the first flight since the overhaul. The pilot departed Runway 06 at Valdez, and climbed to about 1,000 feet above the ground, when the engine suddenly quit running. He said he restarted the engine, but it only ran another 45 seconds before stopping again. The pilot selected an emergency landing area on a highway, but had to slip the airplane to avoid several vehicles on the highway. The airplane collided with a power line, about 25 feet above the ground. The airplane then descended to the ground and received damage to the right wing, the right wing spar, and the landing gear. On April 16, 1998, a Federal Aviation Administration (FAA) airworthiness inspector, Anchorage Flight Standards District Office (FSDO), reported the pilot/mechanic had completed a disassembly of the engine. All of the engine cylinders were scored. The pilot had installed chrome cylinders, and during the assembly, he applied a coating of light grease to each engine cylinder bore. The engine then was temporarily stored before being installed on the accident airplane. According to the FAA inspector, the engine cylinders required an application of a thicker grease than what was used by the pilot.