Again FWIW, in today's unending varied science of internal combustion engines & unending discussions of same:
1. After performing smoothing out my new Model A intake manifold stated in above paragraph (2.) of above reply no. (10), rather than boring out my new Model A intake manifold with the recommended approximately 1.25" for use with a B carburetor, I experimented using a Dremel tool to open only the bottom end of the intake manifold to approximately 1,25" where it meets the larger Model B carburetor flange & larger Model B carburetor gasket.
2. When looking at this end of the intake manifold opening, near the carburetor, it resembles looking at a Model A or Model B carburetor venturi with an opening that resembles the flare at the end of a trumpet, thus allowing a rapid opening of unobstructed flow from the larger diameter B carburetor into the A manifold.
3. As far as how this particular intake manifold airflow shape & setup works, i.e., to have the fuel/air mix going through that which somewhat resembles a double venturi, one above the carburetor & one inside & below, I honestly have no idea what would be the result if tested to verify results on a dynamometer. I just did it my way.
4. In my opinion, designing internal combustion features are similar to today's empirical design used to make today's gunpowder for rifles & artillery weapons; i. e., make a different batch of gunpowder, shape the shell's internal chamber, then ignite it -- afterwards, "wow" -- check the shell's internal chamber psi and the muzzle velocity with delicate calibrated instruments to observe the results by trial & error -- thus being somewhat similar to internal combustion engine trial & error designs, while using a dynamometer for documenting the varying end results.
5. Today's internal combustion engine design has not yet reached perfection -- like in the 1930's, there will always be room for performance improvement -- just good to share what works & what does not.
