850 cfm proform carb on 318!!!!

What kind of conventional thinking does it go against? The reason the generic formulas are used is because on a street car, where engine speeds and throttle opensing are all over the place. The bigger cfm will always make the most horsepower. And at full throttle, they won't give up much. It's not as mnuch about the 50% "seeing" but rather the fairly steady throttle opening and ever-increasing rpm (until shift point is reached). I think what you will find if you run a wide band O2 is that at low engine speeds and part throttle, the big carb can't mix fuel well. So the response is sluggish, the mileage sucks, the plugs get fouled earlier, the idle isn't as controlable or good, and the smaller carb would work better. Pretty much any drag race engine will do better with a typically "overcarbed" situation. Street cars don't.