A lot of people get caught up in the "big-small" thing. What it boils down to, is quality of flow. A smooth, clean flowing port is what you are after. Turbulence causes a port to act smaller. Think in terms of gentile changes in directions. A toboggan run is what you're after in a flathead. Think in terms of inertia, what would happen if you dropped a marble down the intake ( OK, a marble small enough to fit through the valve lift). The valve lift is a part of your intake track as well! The least amount of turbulence. How does the mixture pass through the valve and transition into the cylinder? Barney Navarro had it together back in the 40's. Check out Ron Main's Flatfire. If a bigger valve can do this, cool, don't toss anything out without looking at the entire picture, twice!