An engine comprises at least one cylinder, at least one piston reciprocatable within the at least one cylinder, at least one intake port through a wall of the at least one cylinder, at least one exhaust port through a wall of the at least one cylinder, at least one reciprocatable sleeve valve within the at least one cylinder for controlling porting of one or both of the at least one intake port and the at least one exhaust port, at least one shaft configured to be rotated by reciprocal motion of the at least one piston, a piston drive means coupled to and reciprocatable with the least one piston and a sleeve valve drive means coupled to and reciprocatable with the at least one reciprocatable sleeve valve. An axis of reciprocation the sleeve valve drive means is spaced from and parallel to an axis of reciprocation of the piston drive means of the at least one piston and the axis of reciprocation the sleeve valve drive means is positioned around the circumference of the shaft from the axis of reciprocation of the piston drive means of the at least one piston. This may allow the engine to be more compact and have a reduced physical size compared to some known engines.