The 200-hour private pilot was conducting a local sightseeing flight. Approximately twenty minutes after departing, the pilot reported hearing a loud bang and the engine began to run rough and lose power. The pilot located a private airport in close range and flew directly to it under partial power. Since he was high, the pilot decided to make a circular pattern to lose altitude. When he lined up with the runway, the airplane was still too high to land and the pilot elected to use full flaps and a slip to lose altitude. The pilot realized he was going to overshoot the runway and he pulled up and added full power. The engine continued to run rough and the airplane was still losing airspeed and altitude, so the pilot decided to make another approach from the opposite direction, approaching from about 25 degrees to the right of the runway. Full flaps and a steep approach were used to lose altitude and the airplane touched down approximately two-thirds of the way down the 2,700 foot turf runway. After touching down, the pilot applied both brakes and the airplane skidded to the right, causing the right wing to come into contact with a hangar. The airplane nosed over and came to rest in the upright position. Examination of the engine revealed a crack at the number one cylinder.