Abstract: In an internal combustion engine intended to provide high fuel economy, low noxious emissions and high power, a pair of four cycle power cylinders are alternately fed by a two cycle charge cylinder in which a rich air/fuel mixture is compressed and delivered alternately to variable volume charge chambers communicating with the power cylinders, the three cylinders operating off a common crankshaft. A lean air/fuel mixture is inducted to each power cylinder on its intake stroke. Ignition occurs in the charge chamber and the flame front moves therefrom into the lean mixture in the power cylinder. The volume of the charge chamber may be varied in response to power requirements of the engine. A valve between the charge cylinder and charge chamber blocks flow therebetween during ignition and provides a restricted orifice between the charge chamber and power cylinder during the compression stroke controlling flow therebetween.