Circumstances
Prior to departure, the airplane had been refueled with 37.5 gallons of 100 low lead fuel. Shortly after takeoff from runway 23, the pilot heard a pop/bang from the engine, and the engine seemed to lose power. The pilot also felt a severe vibration after the noise. He executed a 180-degree left turn in an attempt to return to the airport. Subsequently, the airplane landed in a grass field, impacted a dirt embankment and a fence, and came to rest upright in a ditch.
Examination
Examination of the aircraft revealed that the throttle cable was routed above the rear mounted alternator belt, and the cable was resting on the alternator belt. The throttle cable shielding was worn through by contact with the alternator belt, and the braided cable was exposed. However, no damage was noted to the braided throttle cable itself. One of the tubes of the engine mounting frame was fractured; the fracture surfaces were consistent with an overload failure.
Engine Test
Mechanical continuity throughout the engine was established when the propeller was rotated by hand. The engine was then test run on the airframe for approximately 1 minute at an engine tachometer speed of 1,300 RPM. No anomalies were noted with the engine during the examination and test run.
Conclusion
The reason for the partial loss of engine power could not be determined. A review of the airplane's logbooks revealed the airplane underwent annual and 100-hour inspections between the time the overhauled engine was installed on the airframe and the accident.