Abstract: An external combustion engine comprising a body (8), at least one working chamber (18), combustion chamber (13), crankcase (21) and compression chamber (6), at least one working piston (20), compression piston (7) and crank mechanism (22), and a valve gear and a heat exchanger, and wherein the required air is drawn by suction from the air surrounding the engine via valves or equivalent. After the working cycle, the expanded hot air is directed from the working chamber (18) through a valve (12) or (24) past the heater (17) into the combustion chamber (13), to be used as combustion air.