On March 7, 2008, about 1500 Pacific standard time, a Maule M-4 airplane, N51430, sustained substantial damage following a loss of engine power, forced landing and intentional ground loop at the Eastern Sierra Regional Airport, Bishop, California. The airplane was being operated as a visual flight rules (VFR) cross-country flight under Title 14, Code of Federal Regulations Part 91. The private pilot, the registered owner/operator of the airplane, and two passengers were not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The pilot departed about 1455 and his intended destination was Columbia, California. The airplane sustained substantial damage to the right horizontal stabilizer and right wing. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on March 10, the pilot reported that just after takeoff the engine began "running really rough" and he returned to the airport for a landing on the departure runway. He reported the airplane touched down long and overran the runway. The pilot stated he intentionally ground looped the airplane in an effort to avoid a fence located beyond the overrun area off the runway. The airplane's right main landing gear collapsed during the intentional ground loop. Post accident examination of the engine by a Federal Aviation Administration (FAA) inspector (Reno Flight Standards District Office [FSDO]) and an airframe and power plant mechanic revealed that the alternate induction air valve (automatic air door) was separated from the induction bracket and a 2-inch-long AN3 bolt associated with the assembly was lodged between (holding open) the number six cylinder exhaust valve and exhaust port. The corresponding door hardware, a spiral spring, washer, and cotter pin were not found. The FAA inspector reported that he believes the unfound hardware passed through the engine and out the exhaust. Maintenance logbook records showed that an annual inspection of the engine was completed on December 28, 2007. No maintenance discrepancies or anomalies with the alternate air valve were noted. The pilot reported that there were no discrepancies related to the alternate air system prior to the accident flight.