The testing is done and we’ve proven our point that the printed CFM Ratings supplied by the Rochester Products Division (RPD) of GM has been incorrectly documented from the very beginning… Realize, that compared to the equipment that is available today, RPD was using antiquated equipment and more theory than actuality in determining their flow numbers… And unlike Holley & Carter who used cfm ratings as part of their performance marketing campaigns, GM (RPD) actually would have preferred not using any CFM Ratings with their carburetors at all… The Small Base Rochester 2 Barrel Carburetor CFM ratings that we have proven, comes from the differences in the diameter of 5 different models that range from 1″ up to 1.250″…  My Thanks go to Nick Smithberg @ Smithberg Racing for having the skill, the equipment, and the want to do this project with us… Nick tested all of the 5 sizes; using multiple pressure drops and flows; and all testing was done with and without the air horn bell for comparison.2GC - 1 3:32" VENTURI