[Barry_R]

Originally Posted by olddog

To the original question, on carb sizes, I was surprised by the answers.

471 cid at 6000 rpm would pull in 818 cfm at 100% volumetric efficiency.

Why so much carb?

Because whatever carb sizing formula you are using is woefully inaccurate, and most likely based on poor assumptions regarding flow measurement. Carbs are rated at a predetermined amount of vacuum drop below the plates in order to define a comparative value. The vacuum drop rating number (1.5" on 4 bbls) was derived from limitations of the flow testing equipment, and not from any particular engine driven value. That number really has only a passing nominal relationship to the air handling demand of the engine.

Ford and others were quite cognizant of this even back in the 60s when tehy installed multiple carbs on otherwise modest engines.