Abstract: An internal combustion engine is provided with an improved throttle structure. The engine includes a carburetor having an air passageway in it, and an intake manifold interposed between the engine and the carburetor, the carburetor being attached to the intake manifold by any convenient method. The intake manifold includes at least one wall defining a plurality of fluid passageways operatively connected to the carburetor and to the combustion chambers of the engine. In the preferred form of the invention, a cylindrical tube has an axial length chosen so that a first end of the tube extends into the carburetor while a second end extends into the intake manifold. The second end of the tube and the intake manifold define the throttle valve for the engine. The tube is mounted for movement between at least a first closed position where the second tube end is adjacent the wall of the manifold and a second open position where the second tube end is remote from the wall of the intake manifold.