I always like to hear this big lazy port vs a big well designed port kind of discussion. What makes the port to big or even to small? Depending on if we are basing this off for every engine or a particular combination. Big port on small cubes is going to need a lot of rpm to make port efficient. It might never become efficient if you can't spin it high enough. A big ci motor is different. More ci will move more air at a lower rpm vs a small ci. But it also depends on how many rpms, both engine sizes, and rpm. Rpm is cubic inches also.