Abstract: The cylinder head for a twin V-twin motorcycle engine contains an intake port entrance lies in a plane oriented at an angle of less than ninety degrees to another plane defined by the center lines to the intake and exhaust valve guides and the entrance is characterized by a rectangular shape that is tilted from the horizontal plane of the head so that one of the three corners to the rectangular shape is lower in vertical position than the other three. The floor, the lower side between the two lower most corners, is oriented perpendicular to the intake valve guide.

Abstract: Greater torque and power are realized in V-twin motorcycle engine with a cylinder head having a combustion chamber that incorporates two flow relief areas, one for each of the intake and exhaust ports, located on opposite right and left sides of the combustion chamber, and flow resist areas about the remaining portions of the respective port's periphery, obstructing gas flow into the flow resist areas. The foregoing arrangement defines a gas reversion path from the exhaust port that zig-zags through the chamber to the intake port, increasing the length of the path and reducing the adverse effect of reversion. A rectangular shaped intake port entrance and an accompanying rectangular shaped manifold passage provide for input of greater volume of combustible gas and a D-shaped exhaust port exit contribute to the effectiveness of the combination.