Abstract: A two piece intake valve for internal combustion engines comprising an inner and an outer valve which can be designed with orbicular heads. The inner valve including a stem of a smaller outer diameter than the outer valve. The outer valve including a hollow stem large enough to accept the inner valve stem, an inner valve guide, and an inner valve control spring and retainer mechanism. The outer valve also including a valve seat in the center of its bottom face to seat the inner valve. The head, or base, being equipped with one or more vents which communicate between the intake port and the combustion chamber and being releasably opened and sealed off by the inner valve. The vented valve unit incorporating an independent actuation means by way of pressure differentials created by the induction cycle, and/or directional inertia factors of the mechanically controlled valve element. The vented valve unit also incorporating design features to effectively control and dampen inner valve closing.