On April 30, 2007, about 1145 Pacific daylight time, a Cessna 177RG, N177R, experienced a loss of engine power and impacted trees during a forced landing near Perris, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, sustained minor injuries; the airplane sustained substantial damage. The cross-country personal flight departed Temecula, California, about 1130, with a planned destination of Fullerton, California. Visual meteorological conditions prevailed, and no flight plan had been filed. The approximate global positioning system (GPS) coordinates of the primary wreckage were 33 degrees 45.25 minutes north latitude and 117 degrees 15.50 minutes west longitude. The pilot reported that he fueled the airplane with 28.22 gallons of 100 low-lead fuel prior to departing. After departure, approximately 12 nautical miles into the flight, the engine abruptly lost power. The pilot decided that he would attempt to land at the Perris Valley airport (L65) a short distance away. The accident site was 2.51 nautical miles away from L65. Investigators from the FAA and Textron Lycoming arrived at the site on May 1, 2007, to examine the airplane with assistance from Aircraft Recovery Service personnel. They reported that the airplane had initially contacted a stand of trees, continuing along an energy path where the airplane struck the ground and came to rest at the base of a large tree. During the engine examination, investigators noted that the cap and harness assembly of the single drive duel magneto separated from the magneto. Closer examination revealed significant fretting signatures where the cap is seated against the housing of the magneto by four screws. There were no screws observed or found. There were no impact energy damage signatures on the cap, magneto, ignition harness, or firewall. The FAA coordinator interviewed the pilot who told him that he was the last person to have the magneto harness off of the magneto.