Technical 2 BBL Carb suggestions for a flathead, Rochester 2G, Carter BBD, Stromberg WW , others??

Just saw this.

Generally, the "flange" size refers to the accepted S.A.E. naming convention for carburetor flange sizes. The threes sizes most often encountered would be:

Size 1 known as a "1 inch" carburetor, with a throttle bore generally 1 3/16 inch.
Size 2 known as a "1 1/4 inch" carburetor, with a throttle bore generally 1 7/16 inch.
Size 3 known as a "1 1/2 inch" carburetor, with a throttle bore generally 1 11/16 inch.

None of these have a unique mounting bolt spacing.

The throttle bore would represent what you call butterfly opening.

And you mentioned the venturi, generally referring to the main venturi, which is the smallest diameter of the bore of the major bowl casting. There will also generally be an additional one or two "venturi booster rings" to accelerate the venturi air velocity:



The main venturi diameter is the most critical of a number of conditions that effect air volume.

In the drawing, number 2 is the place the main venturi diameter would be measured.
Number 1 is the throttle bore, and numbers 3 and 4 are booster venturii.

Easy to see the venturi effect by observing the heights of the water column connected to the various points in the casting.

Jon.

 

Yes! That is true. We will see in a couple of months