On April 18, 1995, at 2030 mountain daylight time, a Cessna T210L, N1664X, collided with trees, transmission wires, and a fence during a forced landing near Estancia, New Mexico. The commercial pilot received minor injuries and the airplane sustained substantial damage. Visual meteorological conditions prevailed for the Title 14 CFR Part 135 on demand cargo cross country flight and a VFR flight plan was filed. The operator was B & M Enterprises, Inc., dba New Mexico Flying Service of Albuquerque, New Mexico. During personal interviews, conducted by the Federal Aviation Administration (FAA) inspector, with the pilot, and a review of Albuquerque Air Route Traffic Control Center (ABQ ARTCC) data, the information in this paragraph was revealed. En route from Alamogordo, New Mexico, at 2016, radar contact was established and VFR flight following was received. At 2026, the pilot reported a total loss of engine power and declared an emergency. The controller issued the location and distance to the nearest lighted airport. Radar contact was lost at 2029; however, at 2031 the pilot transmitted that the landing would be in a field. Dark night conditions precluded visual contact with the terrain. On final approach, with the landing light on, a tree and houses were observed. At 50 feet above the ground, the pilot deviated to avoid the houses; however, the airplane descended through power lines and impacted the terrain. The airplane came to rest inverted along a fence row. Structural damage occurred to the left horizontal stabilizer, rudder, fuselage,and wings. An examination by the FAA inspector and the manufacturer representative revealed a hole in the #2 piston. The #2 cylinder exhaust valve head was separated from the valve stem and the head was not located. Physical evidence indicated that the exhaust valve head migrated out the exhaust. Metal parts, found in the oil sump, were identified as parts of the #2 exhaust valve seat. Damage was noted to the turbine section of the turbocharger. A review of the maintenance records revealed the following information. Engine S/N 217105R was overhauled in March, 1992; however, records did not show that the valves had been changed at the overhaul. According to the manufacturer representative, "guidelines for an engine overhaul require changing the valves." Records further indicated that the engine was removed in August, 1993, due to a cracked case and subsequently reassembled. Cylinders #4 and #6 were replaced in November, 1993, and a compression check conducted in December, 1993, indicated "68" for cylinder #2. The engine was again removed, disassembled, and reassembled in February, 1994, with the #4 cylinder being replaced, and in September, 1994, the #3 cylinder was replaced. On January 28, 1995, the last recorded maintenance record of an engine compression check indicated below "60" for 4 of the 6 cylinders.