Jon Richard wrote:

When you say the size of the openings are you referring to the physical dimension of the booster venturi itself where the annular fuel discharge holes are housed?

I am referring to the holes on the under side of the main booster body next to the tubes.  In this pic I borrowed from the net it is the hole that is under the vertical arrow.

 

I received a PM that I thought others would be interested in:

Daze
Thank you for your information on carbs! Can you help clarify an item. It is my understanding that Hipo mustangs had 1.12 Venturi's but a different primary. This is what gave the horsepower without sucking all the gas! Otherwise it's very inefficient. Seems by reducing the Venturi you made a 1.08 but would still have the issue with the primary?
Thank you!

Besides sleeving I plan to change jet size and boosters.  The smaller venturi will allow for better throttle response.  I have also purchased smaller jets for my carb, I went from 55/64 to 48/55.  the third piece to this puzzle is the boosters.  The ones that came on my carb, especially the one from the secondaries has huge booster tubes.  I plan on first trying it with these boosters and then I will swap them out for a combination of boosters with smaller tubes.  I got two different booster sets off of a some two barrel carbs I had for parts.  It will be more trial and error than exact science but I think if I go with the smallest booster I have in the front and the next biggest in the back I can probably get it close.

I have not yet gotten around to rebuilding the carburetor I have to do a real test.  I have sent out two sets of these to other people to test (4-5 months ago) and have never herd back from them.  This project is stalled until I either find the time to rebuild the the carb I have or unless I hear back from those that said they were willing to test for me.

Daze, I may have found a solution for figuring out what the jet sizes should be. The Summit Racing M2008 series carburetor is the grandchild of the Autolite 4100. I won't go into the details on how that came to be, there are many forums that discuss it in detail. 
The interesting thing I suspect would be helpful for you is that the Summit carb's annular booster can be used in a vintage Autolite 4100. 
Why is that important you ask? Well the Summit booster features replaceable jets for both the accelerator pump discharge and the idle feed.

What I am envisioning is that you drop a Summit booster into a 4100, make the jet adjustments per what the vehicle needs and either leave the booster in or braze and drill out your old booster to the match sizes you used on the Summit booster. 
I am certain that there would be flow differences between the Summit booster and the vintage 4100 booster. It would mostly affect vacuum signal and idle circut.

The one problem with this idea is that Summit will not sell a booster by itself. You would have to buy the entire carburetor.

Here is another idea.
The smallest Summit M2008 carb is 500cfm. Without measuring, my guess would be that the venturi is close to a 1.08. Summit also makes a 600 and 750. The 600 is probably comparable to a 1.12 venturi 4100 (I am guessing here). The 500 cfm carb would be ok-ish for a mild build 302 small block. 400-350 cfm would probably be better. 

Your venturi restrictor in a new 600 cfm Summit carb might be the best of both worlds solution. Adjustable jets, annular booster goodness, large go fast vacuum secondaries. And you don't have to find and  completely rebuild an overpriced worn out 4100.

Last edited by Farnsworth (8/24/2017 2:06 PM)