Have several carbs to choose from, box of 2100, couple AFB and a 4100.

Narrowed down to Autolite 4100 1.08 or Carter 400 CFM AFB. Already have both. Will be mounted on Offy DP (yes, aware of East West orientation and small primary runners). Mildish cam, split EFI exhaust. Daily driver truck.

Both are complete but in need of soda blast and refurb, will be using mech choke, mounted on 1" spacer (polymer - Texas heat) and will need linkage worked out.

Either would be a good choice.

Annular discharge, adjustable vac secondary and Holley jet compatibility with 4100?

Metering rods, mech secondary with AFB?

if you had both, which one is preferred?

 

The trouble with old carbs is that you inherit all the changes that have been made by every person who has rebuilt a particular carb in the 40+ years since it was made. I used to buy, rebuild, and sell 4100's. The problem I ran into is that there is no book or chart listing the # of each discharge cluster so that you can check and make sure you have the right cluster on the right carb. The chances are that during the life of that carb some happy rebuilder wanted to try a different cluster on that carb, or he just got it mixed up with a diff. carb. If it has been changed, then you'll most likely have to recalibrate the air bleeds, the accelerator discharge orifices, etc. And then there is the throttle shaft to consider. After a long life, the shaft has most likely worn into the body of the carb and created a vacuum leak, making tuning impossible. (That applies to both carbs).

Both are excellent carbs. You might get lucky and find that your choice is perfect. Or, you can spend hours rebuilding, tuning, swapping jets, etc. and never get it to run right. Why not bypass all the risk, sell them both on ebay, and use the $ to offset the cost of brand new carb. (If that 4100 has a Z in the serial # it came on a mustang and is highly sought after by builders looking for an oem mustang carb. Summit now sells the grandchild of that 4100 for about $340. Edelbrock makes a great variation on that AFB carb. Good luck.
P.S. I wanted to add that if you're concerned with heat and vapor lock, the physical design of the 4100 will place the primary bowl right above the exhaust manifold, whereas the AFB has the bowls toward the firewall and the radiator, and out of the heat flow.

 

All good points. The AFB may or may not have been tweaked by previous owners. No idea on the metering rods.

The 4100, unlikely. The carb is a 1957 from a Y block 312. The booster numbers are 1 and 3.

 

That's not even a question for me. I'd use the 4100. The AFB is a fine carburetor, and I've used em, but I like the absolutely brain dead simple design of the 4100.