Carter AFB Carburetor


AFB Carburetor Identification

AFB Identification

Look for 4 numbers followed by a S. Example 3445S. You may find other numbers stamped on the carburetor, but they are usually the part numbers of the part they are stamped on. An example would be 0-1654S.

The AFB (Aluminum Four Barrel) carburetor was produced by Carter for original equipment cars from 1957-1971. The AFB was then available as a high performance 9000 series carburetor up until the late 1990’s. Weber is currently making the AFB now known as the Edelbrock.The accelerator pump controls response when pressing down on the gas pedal. Too little squirt will cause a flat spot or hesitation, too much squirt can cause black smoke and/or sluggish acceleration. You can change the action of the accelerator pump by repositioning the accelerator pump linkage.The metering rods are of a step design and are controlled by vacuum and metering rod spring action. At low speeds the metering rodis dropped down into the primary main jets, thus partially closing off the flow of fuel. At higher speeds and less vacuum the rods pull up from the main jets allowing more fuel to flow.AFBs use mechanical secondaries. Punch the gas pedal and the secondaries will open.The early AFBs were not rated with CFM statistics, but the later performance 9000’s were.Learn more about the metering rods, jets and metering springs. See all of our AFB parts
Carter AFB Jets, Metering Rods & SpringsAFB Jet & Metering Rod Sizes

Carter AFB Exploded Diagram


CFM Venturi Diameter Bore Diam
3721 575 1 1/4 1 9/16 1 9/16 1 11/16
4121 1 1/16 1 1/4 1 7/16 1 9/16
4122 1 1/16 1 1/4 1 7/16 1 9/16
4132 1 1/16 1 9/16 1 7/16 1 9/16
4133 1 1/16 1 9/16 1 7/16 1 9/16
4136 1 1/16 1 9/16 1 7/16 1 9/16
4137 1 1/16 1 9/16 1 7/16 1 9/16
4147 1 3/16 1 9/16 1 9/16 1 11/16
4148 1 3/16 1 9/16 1 9/16 1 11/16
4204 1 3/16 1 9/16 1 9/16 1 11/16
4205 1 3/16 1 9/16 1 9/16 1 11/16
9400 400 1 1/8 1 1/4 1 7/16 1 7/16
9500 500 1 3/16 1 1/4 1 7/16 1 11/16
9501 500 1 3/16 1 1/4 1 7/16 1 11/16
9510 500 1 3/16 1 1/4 1 7/16 1 11/16
9511 500 1 3/16 1 1/4 1 7/16 1 11/16
9625 625 1 3/16 1 9/16 1 7/16 1 11/16
9626 625 1 3/16 1 9/16 1 7/16 1 11/16
9627 625 1 3/16 1 9/16 1 7/16 1 11/16
9635 625 1 3/16 1 9/16 1 7/16 1 11/16
9636 625 1 3/16 1 9/16 1 7/16 1 11/16
9637 625 1 3/16 1 9/16 1 7/16 1 11/16
4758 500 1 3/16 1 1/4 1 7/16 1 11/16
4759 625 1 3/16 1 9/16 1 7/16 1 11/16
4760 750 1 7/16 1 9/16 1 11/16 1 11/16
4761 500 1 3/16 1 1/4 1 7/16 1 11/16
4762 750 1 7/16 1 9/16 1 11/16 1 11/16

Carter AFB Pump Link

Tip – The AFB pump link, links the pump lever to the accelerator pump. When you look at the link installed from the front of the carburetor, it should look like a ‘S’.

Free Carter AFB Manuals

Please do not distribute these manuals, but please feel free to give out the link to this page.

Carter AFB Carburetor Manual

Application Carburetor
V8 Fairlane, 500, Custom, 300, Police Interseptor 1957
2441s, 2441sa
V8 Montclair, Monterey, Station Wagon & Turnpike Crusier 312 1957
2441s, 2441sa
1966 Chrysler, Dart, Dodge, Plymouth 4121s, 4211s, 4132s, 4133s, 4136s, 4137s
1966 Lincoln 4147s, 4148s, 4204s, 4205s


AFB Accelerator Pump Problem & SolutionThis is a problem that one of our customers reported to us along with the email conversations.Sorry to bother you. I bought kit 4011 for my 1958 Cadillac Eldoradro, Carter 2862S AFB carb. Can’t get car to come off idle, wants to die. Warm, choke off. Idles O.K., 500-850RPM O.K. But when I push the accelerator to increase the RPM’s avove 850, it wants to die. If I coax it past this spot, at higher RPM’s it seems fine. A stream of fuel comes out the two accelerator pump jet nozzles when I depress the throttle, so I think the accelerator pump is O.K. I’ve adjusted the two mixture screws. There is a big air adjustment screw located between the two idle mixture screws, I tried to adjust that also. (But I don’t actually know the procedure for this air adjusment) Once it starts getting past the stumble, I notice drops of fuel coming out of the primary venturi’s, and dropping down onto the throttle buterflies. (I would think it would be atomized, not drops?) I’ve disassembled the carb a couple times, the float bowls are about 1/2 full. I’m stumped, I didn’t have this problem before I rebuilt the carb. I didn’t remove any shafts or butterflies. I would appreciate any ideas you have to offer. Second update: I should have checked this before I sent My first e-mail. My problem is a lean condition. If I pour a lttle gas down the carb while it is stumbling, itstops stumbling and smooths out. So the question is: What causes a just above idle lean condition? Third update: I fully closed the big air adjustment screw located between the two idle mixture screws, and this helped alot. I moved the accelerator pump rod down to the bottom hole, and this seemed to help some. I stll have an off-idle stumble, but it’s driveable, it doesn’t try to stall, just stumbles. The stumble is smooth slow acceleration, not punching it.
I took it apart again, and found a piece of debris partially plugging the small brass tube
feeding fuel to the primary venturi, (the small tube inside the bigger tube with holes in it)
The clue was, just above idle fuel would drip out of one venturi, (the bad side) No more hesitation, and I was able to open the air adjustment screw to set the idle speed.


Watch Our AFB Rebuild Videos

I recently purchased a leather accelerator pump for my Carter afb. I
soaked the leather in 3 in 1 oil overnight and installed the new pump
but am still a little unhappy with the pump shot. I have never been
able to get a very strong pump shot, even after adjusting the stoke
and installing the arm with the three holes since my carb did not have
the holes, only a single hole. Are there any tips or tricks to get a
stronger pump shot, there is currently a steady stream but it does not
seem to have any force behind it. I have two afbs and they both have a
very similar pump shot, somewhat weak. Is this just typical of afbs? I
noticed the Edlebrocks pump shot is substantially stronger and this is
basically the same carb, perhaps they upgraded it at some point. I am
still dealing with my off idle stumble and believe it may be a lean
condition due to weak stream from the squirters.

One odd thing I did notice. I swapped the two accelerator pumps from
my two afbs. While one pump inserted smoothly and tightly into the
well, the other pump would not, as if the well was a smaller diameter,
it seemed to bind up in the well. .The pump from the other still
worked well in the other afb. Confusing since both pumps appear to be
the 11/16 leather cup.

Any insight would be appreciated.

I have never compared an Edelbrock to and AFB squirt and that wouldn’t be a very good way to judge anyhow. If you are concerned about the main discharge not discharging enough, make sure the small passages are clear. Ethanol will leave residue in the carburetor passage ways. You will have to poke through the holes with wire. Test the pump before putting the top back on. Take a look at the Carter YF technical page. There is a video there on how to test the accelerator pump. Same idea for the AFB.

Soaking a leather pump in oil is not the best way to ready an accelerator pump and I’m not sure 3 in 1 oil is what should be used either. There are a lot of chemicals that do not play well with ethanol, so be careful. I keep all chemicals away from any carburetor. Only add 1 to 2 drops of regular oil before installing. Soaking in oil overnight probably has the leather swelled up past where it should be. I don’t know if the gas will eventually bring it back to a natural size or not.

Accelerator pumps do not necessarily fit tight in the pump well. Actually most don’t and shouldn’t, or the action will be too stiff.