Then how do you explain volumetric efficiencies over 100%? Which is NOT hard to do.
I don't want to offend you, but it sounds like you know enough to have a decent foundation, but you need to keep learning.
You are caught up in numbers and you treat those numbers like they are cold, hard facts.
I can tell you that I've been told (as I have no desire to race at a place like Denver) by Greg Anderson that he never changed a jet from Denver to Sonoma to Woodburn to Seattle. Didn't change a jet.
There is more to it than your simplistic view of things. Starting with a dual plane intake being better for low speed performance. It's not. Never has been. It's another in a long line of bullshit that keeps getting passed around like VD in a high school locker room.
I hope before you buy something that isn't what you really should use, you take some time and start learning about carburation, how they function and what the circuits do. Study Bernoulii and Venturi and see how they apply to carburation.
Or, you can just bolt on what you want and stay your course.
But to suggest you can never have more than 318 inches because that is your displacement is wrong. Competiton Eliminator is a good place to start looking at what small displacement engines are capable of.
Also consider, even if you bolted an 850 on your engine (using an essentially worthless CFM number but that what we are dealing with) you are only using the primary side of the carb most of the time. Think about that. Throttle position makes a difference.
Now, rather that using CFM to select a carb, why not use Venturi diameter? That's a much better way to select a carb.
