A cylinder head assembly and a method of providing an air-fuel mixture from a carburetor to a cylinder of an internal combustion engine are disclosed. The cylinder head assembly includes a cylinder head and a component coupled to the cylinder head. The cylinder head includes a first port having a first passage linking a first end to an intersection, and a second passage linking a second end to the intersection, where the intersection includes an abrupt transition between the first and second passages. The component includes a tongue that protrudes into the first passage from the first end to proximate the intersection, where the tongue is positioned along at least a portion of an inner side of the first passage, and where the tongue is gradually-reduced in thickness at least proximate the intersection.