THE PILOT STATED THAT WHILE AT CRUISE FLIGHT AT 3,700 FEET MSL, HE MADE A POWER REDUCTION IN PREPARATION TO DESCEND TO 3,000 FEET. AT THAT TIME HE HEARD A LOUD BANG AND THE ENGINE QUIT SUDDENLY AND COMPLETELY. NO PROBLEMS WERE FOUND WITH THE FUEL OR THE AIRPLANE'S FUEL OR ELECTRICAL SYSTEMS. THE ENGINE OPERATED NORMALLY ON A TEST STAND, AND WAS DISASSEMBLED AND LATER RETURNED TO SERVICE WITH NO PROBLEMS NOTED.