5 to 4 is a great question. I have been pondering this also. My thought was 4 valves are cheaper and the 430 displacement versus 360 gives them more horsepower anyway. Maybe they went to varible valve lift to help low end torque. Also they could add the fifth valve in the next model for more punch. Just a quess Does anyone know if the F430 has varible valve lift in addition to timing? Lee