On March 23, 1994, at 1530 hours Pacific standard time, a Cessna 172M, N13620, lost power and collided with trees in mountainous terrain in the Los Padres National Forest about 13 miles east of Santa Maria, California. The pilot was conducting a local visual flight rules personal flight. The airplane, operated by Horizon Aviation, Spring, Texas, was destroyed. The two Dutch certificated pilots received minor injuries. Visual meteorological conditions prevailed. The local flight originated at Santa Barbara Municipal Airport, Santa Barbara, California, about 1445 hours. The pilot stated the airplane's engine lost power. As the airplane descended into a canyon, the pilot realized he was forced to land and selected a tree to collide with to attenuate the impact forces. The airplane came to rest inverted. Both pilots egressed unaided and manually switched the emergency locator transmitter on. The pilots then hiked out of the wilderness region and were found by rescuer's searching for the ELT signal. The National Transportation Safety Board interviewed the airplane's pilot the day after the accident. The pilot indicated the loss of power was gradual with engine roughness. The propeller continued to windmill after a total loss of power. The pilot made several attempts to restart the engine. The pilot indicated he checked the fuel selector, moved it from right to left several times, and also manipulated the mixture control. According to the pilot, the engine would start but would not continue to run. The pilot did not indicate whether or not he manipulated the magneto switch during the attempted engine starts. The airplane's engine, a Lycoming O-320-E2D, was examined on June 6, 1994, at the El Monte Airport. Scoring was noted on the right and left magneto pads next to the mounting clamps. The clamps were found tight and the scoring appeared fresh due to the lack of dust and other debris found in the area adjacent to the scoring. It could not be determined if the scoring on the magneto mounting pad was preexistent to the accident. The left magneto, a Slick model 4201-R, was found at 45 degrees before top dead center (BTDC), 20 degrees in advance of the 25- degree setting specified in the airplane's service manual. The left magneto internal timing was checked. The contact point gap was measured at .005 inches. This measurement exceeds the manufacturer's specified range of .008 inches to .012 inches. Further examination of the magneto revealed the breaker cam and the contact points were worn. According to the engine manufacturer, the left magneto, the Slick model 4201-R, is not approved for installation on Lycoming engines. The Slick 4201-R is approved for installation on several series of Teledyne Continental engines. The right magneto, a Slick model 4270, was found at 30 degrees BTDC, 5 degrees in advance of the 25 degree setting specified in the airplane's service manual. The right magneto internal timing was found to be within the manufacturer's specified range. The pilot operating handbook for the Cessna 172M provides a checklist and amplified procedures for coping with emergencies. The handbook states: "A sudden engine roughness or misfiring is usually evidence of magneto problems. Switching from BOTH to either L or R ignition switch position will identify which magneto is malfunctioning. Select different power settings and enrichen the mixture to determine if continued operation on BOTH magnetos is practicable. If not, switch to the good magneto and proceed to the nearest airport for repairs." Review of the airplane's maintenance records revealed the engine was overhauled on August 19, 1993, about 265 flight hours before the accident. There was no evidence found in the aircraft maintenance records to indicate that new or overhauled magnetos were installed at the time of the engine overhaul. There also was no evidence found that the either of the magnetos were replaced after the engine overhaul. The last entry in the airplane's engine logbook, dated December 30, 1993, about 78 flight hours before the accident, indicated the magneto timing was adjusted.