I like AFB carbs. I am not sure why, probably because so many people seem to hate the later Edelbrock versions, in particular the 1407 that have a terrible off idle lean spot after the transfer slot is fully exposed but the main circuit has not started flowing.

I got this one for $125 with an air cleaner. I know I overpaid, but it was close to home and I wanted to sell the bling setup on my car that would not fit under the hood.

The previous owner of my car was very optimistic in his description of the engine, so eventually I got a stockish 440 for it that has way too much piston to wall clearance, but at least it has camshaft bearings that stay in the block and doesn't leak a quart of oil every 150 miles. .

I never tried this modification before. In the past I just used a wire in to reduce the air bleed area.

A little more material removed.

A little more with a dremel

I think this will be enough to change air bleeds without removing the cover.

not sure what you're trying to do but the idle air bleed and idle jet size are pretty close on those carbs, keep in mind there are more than one bleeds that feed air to the idle circuit. afb's have more air bleeds and emulsion bleeds than holleys. the main metering on those edelbrock electric choke carbs is too lean. the idle jet should be around .037" but can be opened up to .040" if need be.

I'd be interested to see what the air bleed changes are worth. I raced my car 8 years with a pair if 1407s. There was definitely an issue leaving off the foot brake even at 3000 rpm. Getting ready to run these carbs on my sons racecar. I've opened up the secondary well feeds. Tried heavy/light air doors. Various squirters. Raised the float levels. Run the idle fat. Never messed with the idle restrictions or bleeds. Never messed with the transfer slot location. At times we ran quick. But not near as consistent as the Holley's.
Doug

This is a neat post!

The CarterBrocks are not bad carbs, it's just that their tunes are antiquated and they are much more work to dial in than their competitors. Just like you are finding out.

Can anyone answer why they have never done any updates to their circuits when their problems are so well known?

the size of the idle jet can be a big deal on these carbs. i would think the more plenum volume the more critical this can be off idle. i don't think the passages from the jet to the main wells in the edelbrocks are as large as the old afbs. comparing emulsion tubes on the edelbrocks to the old afb/avs is an eye opener for race builds. the edelbrocks and older afbs have a lot of places where they introduce air in the fuel stream and some of that can be blocked in a race car. juggling the secondary opening rates with the velocity air valves is kind of trial and error. an avs top would make these carbs more ideal for performance, but edelbrock won't sell tops seperately.

Those holes will disturb the airflow into the primary introducing a side shear effecting distribution, no???? It would have been interesting to see an AF ratio before and after mod. Including cylinder to cylinder on a dyno. Carter and the OEM had a lot of different strategies with the AFB. For some of the Chevy versions the anti perc tube was hidden and not exposed above the top.

changing to adjustable air bleeds is not complicated on an AFB

The issue with the late Federal Mogul and Edelbrock 750 carbs is they use the wrong length booster in the primary. If you look at an earlier "correct" Carter 750 you will notice the booster is longer and that places the booster where it actually needs to be which is just after the minimum restriction of the venturii. I have swapped boosters and logged where they begin to flow after the transfer slot slows stops and from memory its was around 500 rpm so thats where the dreaded lean issue comes from. You can raise the float level a little to get the primary booster to flow sooner.

If it were me I would make them have 4 transfer slots 2 pump shot wells and convert them to solid fuel metering. win win win.

Yep that's how its done.

Can you change all of them without removing the cover?

I am not sure.... the holes are big, but are also significantly offset from the main airflow. I suppose the hole could be covered but that was never my intention.

i think the real issues with the added holes is the chance of dirt getting in the air bleed. the added holes really are of no value. plugged/dirty air bleeds make the engine run poorly.

the primary booster actually has two air bleeds that influence low rpm operation. there should be a small brass air bleed on the side of the booster that runs in conjunction with the one on top of the booster.

Why did you do this?