Abstract: A multicylinder reciprocating internal combustion engine with a dual induction system having at least one exhaust poppet valve and a single intake poppet valve for each cylinder, with the intake valve being located so as to control the flow of charge into the cylinder, and with each valve being operated by a rocker arm driven by a pushrod. Each intake port has a vertical dividing wall separating the port into primary and secondary passages, with the primary passages being oriented so as to cause rotational flow about the outermost portion of the cylinder, and with the secondary passages being oriented so as to cause flow directed about a radially inward portion of the cylinder. Flow through the secondary passages is controlled by a number of secondary throttle valves mounted upon a common shaft which extends through the secondary passages, but not through the primary passages.