On August 15, 1995, at 1030 Pacific daylight time, N6854P, a Piper PA-18-150, operated by the owner/pilot, nosed over while taxiing for takeoff near Owyhee, Oregon, and was substantially damaged. The commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed and a visual flight rules flight plan was filed. The personal flight was conducted under 14 CFR 91. In a written statement, the pilot reported that he had successfully performed two previous landings on the dirt airstrip. After the third landing, the pilot stated that he back-taxied approximately 600 feet to the high point on the airstrip and made an abrupt left turn by firmly pressing the left brake. The pilot reported that the airplane began to ground loop and that the nose was slowly going down. The airplane continued nosing over and came to rest inverted. During a telephone conversation with a Federal Aviation Administration Aviation Safety Inspector from the Boise, Idaho, Flight Standards Field Office, the pilot reported that his attention was diverted from looking forward to looking out the side of the airplane for chuck holes during the turning maneuver. The pilot stated that he was not aware that the tail was coming up until the airplane was in the process of nosing over.