THE AIRPLANE EXPERIENCED A TOTAL LOSS OF ENGINE POWER WHILE IN CRUISE FLIGHT. THE PILOT ATTEMPTED TO LAND ON A NEARBY ROAD, BUT WAS UNABLE TO SEE POWERLINES AND A UTILITY POLE OBSTRUCTING HIS GLIDE PATH DUE TO A FILM OF OIL ON THE WIND SHIELD FROM THE RUPTURED ENGINE CASE. THE AIRPLANE STRUCK THE POWERLINES AND POLE AND LANDED IN AN ADJACENT FIELD. EXAMINATION OF THE ENGINE DISCLOSED A FRACTURED CONNECTING ROD CAP AND ROD CAP BOLT IN THE NUMBER 4 CYLINDER. BOTH OF THE CASTELLATED NUTS WERE GONE FROM THE ROD CAP BOLTS. ONE OF THE BOLTS HAD REMNANTS OF A COTTER KEY REMAINING IN THE KEYWAY, THE OTHER BOLT DID NOT. ONE CASTELLATED NUT FITTING A ROD CAP BOLT WAS FOUND IN THE OIL PAN. THE NUT'S NORMALLY SHARP EDGES WERE WORN SMOOTH AND SHINY, GIVING THE APPEARANCE THE NUT HAD BEEN IN THE SUMP FOR A LONG PERIOD OF TIME. THE ENGINE'S LAST MAJOR OVERHAUL WAS 946 SERVICE HOURS PRIOR TO THE ACCIDENT FLIGHT.