Carter AFB maxwedge carb issues

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rebelrouser
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Carter AFB maxwedge carb issues

Post by rebelrouser »

I screwed this one up.
Built an engine for a 64 Plymouth NSS car, engine ran good made 700HP on the dyno, and it ran 10.16 last weekend several times, all steel 3,500lb car. In working on the tune on the dyno, it did not want to idle right. In the past on the Edelbrock Carbs, I have drilled and tapped them for small holley air bleeds to make them adjustable, it seems to work pretty good to straighten out poor idle.
Well these are the original maxwedge long booster carbs and when I drilled them, it caused a couple of the boosters to siphon fuel, lucky the owner had some extra carb parts.
My question is, and I did not even notice until after I drilled them, these boosters have a third bleed on the side, and it intersects the bleed I drilled. These carbs have been discussed on the forum a couple times. Can anybody explain to me the function and need for this third airbleed?
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Ishiftem
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Re: Carter AFB maxwedge carb issues

Post by Ishiftem »

I looked at those carbs when he took them off. For one the transfer slot was nearly 100 percent exposed. That’s one possible reason it idled poorly and had a stumble. You would be better off with the stock idle air bleed size and drilling the butterfly to close the throttle some more. That hole in the side is the primary air bleed. Behind it is what Carter called an economizer jet. You are better off playing with the secondary air bleed on top and leaving that one on the side alone.
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Re: Carter AFB maxwedge carb issues

Post by Walter R. Malik »

rebelrouser wrote: Thu Jul 29, 2021 12:39 pm I screwed this one up.
Built an engine for a 64 Plymouth NSS car, engine ran good made 700HP on the dyno, and it ran 10.16 last weekend several times, all steel 3,500lb car. In working on the tune on the dyno, it did not want to idle right. In the past on the Edelbrock Carbs, I have drilled and tapped them for small holley air bleeds to make them adjustable, it seems to work pretty good to straighten out poor idle.
Well these are the original maxwedge long booster carbs and when I drilled them, it caused a couple of the boosters to siphon fuel, lucky the owner had some extra carb parts.
My question is, and I did not even notice until after I drilled them, these boosters have a third bleed on the side, and it intersects the bleed I drilled. These carbs have been discussed on the forum a couple times. Can anybody explain to me the function and need for this third airbleed?
That side air bleed restriction is after the Idle tube fuel restriction and before the idle cross channel restriction which is before intersecting with the top idle air bleed.
I have never seen one with 3 air bleeds in the cluster idle circuit ... the restriction behind the side air bleed is a fuel/air channel restriction.

The upper tube is the high speed bleed.
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tjs44
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Re: Carter AFB maxwedge carb issues

Post by tjs44 »

Is that a 153 booster?I will be back home next Tuesday and can check if that is what are in my carbs.Tom
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Re: Carter AFB maxwedge carb issues

Post by Geoff2 »

In Carter nomenclature, the hole in the top is the idle bleed; the one in the side is the idle by-pass air bleed. Behind the BPAB, is the Economizer jet which controls air+fuel delivered to the transfer slot.
rebelrouser
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Re: Carter AFB maxwedge carb issues

Post by rebelrouser »

Geoff2 wrote: Fri Jul 30, 2021 6:22 am In Carter nomenclature, the hole in the top is the idle bleed; the one in the side is the idle by-pass air bleed. Behind the BPAB, is the Economizer jet which controls air+fuel delivered to the transfer slot.
So if you want a little more fuel at idle, would you need to reduce both the idle air bleed and the idle by-pass air bleed? The thing was when I reduce the regular idle air bleed size, it caused the booster to siphon fuel. Just trying to understand why that happened.
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Re: Carter AFB maxwedge carb issues

Post by Walter R. Malik »

rebelrouser wrote: Fri Jul 30, 2021 9:45 am
Geoff2 wrote: Fri Jul 30, 2021 6:22 am In Carter nomenclature, the hole in the top is the idle bleed; the one in the side is the idle by-pass air bleed. Behind the BPAB, is the Economizer jet which controls air+fuel delivered to the transfer slot.
So if you want a little more fuel at idle, would you need to reduce both the idle air bleed and the idle by-pass air bleed? The thing was when I reduce the regular idle air bleed size, it caused the booster to siphon fuel. Just trying to understand why that happened.
That alone won't cause that scenario ... there must have been anther adjoining reason for that happening. Excess heat in the fuel percolation, maybe.
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Re: Carter AFB maxwedge carb issues

Post by PRH »

If the air bleed mods resulted in a lower idle speed, and the primary butterflies were opened up a bit to compensate....... it could be that the main circuit has now been activated.
Somewhat handy with a die grinder.
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Re: Carter AFB maxwedge carb issues

Post by Geoff2 »

If you want more fuel at idle, increase the IFR. That is the thin brass tube hanging out the bottom of the booster, next to the larger tube. It will probably be 0.031 - 0.033" if it is still stock. Carter used two air bleeds in the idle cct [ not one as in brand H ] & never advised touching the air bleeds.
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Re: Carter AFB maxwedge carb issues

Post by F-BIRD'88 »

"Tuner". a member on this forum has a good handle on legacy Carter AFB's and the Edelbrocks too.
He may have some helpful info on getting those primary booster clusters dialed in.
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Re: Carter AFB maxwedge carb issues

Post by F-BIRD'88 »

One of the air bleeds also acts as a kill bleed to stop sphioning.
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