Abstract: A configuration of heat engine, a stirling engine, is presented that utilizes an even number of axially opposed, axially aligned cylinders and that can be made using almost unlimited variations in the number of cylinder pairings, size, length, operating temperatures and pressures, materials, heating and cooling sources, etc. The axially opposed configuration of the cylinder pairs maximizes engine efficiency by minimizing dead space, maximizing thermal isolation of the hot and cold sides, maximizing regenerator efficiency, maximizing the free flow of the working fluid and allowing the engine speed (rpm) and power output to be rapidly and precisely altered and controlled. When driven, the engine acts as a heat pump, with all of the aforementioned improvements and advantages over previous kinematic heat pumps and wherein the piston timing can be varied for precise temperature control and to provide a method of defrosting that requires no additional parts or heat source.