Abstract: A tumble control valve for an intake manifold of an engine which eliminates or substantially reduces air leakage between the bottom and sides of the valve blade through a selected rotational segment of the blade as it moves from the closed position toward the open position. The sealed area is maintained by contouring the inner cavity wall to track the arc defined by the bottom edge of the rotating blade. In other embodiments, a flexible flange or wedge-shaped element is attached to the blade to engage the inner cavity wall through the selected rotational segment. In another aspect of the invention, air flow pressure is maintained and tumble is optimized compared to rotational movement of the blade by contouring the top wall surface to track the arc defined by the rotating upper edge of the blade.