Soon after settling in the cruise at 2000 feet, the pilot noticed that the fuel flow was lower than expected. He selected rich mixture but the fuel flow began to fluctuate markedly and the MAP reduced. A short time later the engine began to run roughly, accompanied by a rise in oil pressure and a further reduction in MAP. The pilot elected to return to the departure point. Engine power became inadequate for level flight and the pilot selected an emergency landing area. The aircraft came to rest after running through two barbed wire fences. The engine failed due to long term lack of lubrication to several bearings caused by the rotation of two main bearing shells which covered oil supply galleries. The damage to the main bearing assemblies was such that the cause of bearing shell rotation could not be established.
