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Old 08-06-2012, 05:56 AM
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Testing out AFB's

I am new here on this forum.
I have a 1967 Pontiac Firebird ragtop with a 326 modified a little above stock configuration with dual exhaust with stock exhaust manifolds. I have a Edelbrock performer intake. I had a edelbrock 1405 on top of her, I couldn't get an idle without a miss init, I replaced everything in the carb except the air horn and fuel bowl still woudn't idle, I rebuilt it 3 times in a month til my girl went to go to Church with the car and broke down again. I decided to go back to Carter's and put something ment for a small block Pontiac on it, Not looking for the performance of a Holley. It was recommended I try out a AFB carb, the carb is a 3721SA off a 64 Corvette 327. I have on hand a 3649SA off a 64 GTO 389 and a 4242S off a 67 Firebird 400 and 4028SA off a chevyII 327, I am testing out for the best performance and throttle response.
Installing them on a 67 326, mildly built.
The 3721SA has great idle to part idle response.
the 4242S has great idle to part idle response.
the 3649Sa has good idle to part idle response.
the 4028SA which is a AVS has great idle to part idle response.
They are all 575cfm's and are decent I am wondering which would be the best mix for my 67 Pont. 326?
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Old 08-06-2012, 07:29 AM
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Quote:
Originally Posted by raguza123 View Post
I am new here on this forum.
I have a 1967 Pontiac Firebird ragtop with a 326 modified a little above stock configuration with dual exhaust with stock exhaust manifolds. I have a Edelbrock performer intake. I had a edelbrock 1405 on top of her, I couldn't get an idle without a miss init, I replaced everything in the carb except the air horn and fuel bowl still woudn't idle, I rebuilt it 3 times in a month til my girl went to go to Church with the car and broke down again. I decided to go back to Carter's and put something ment for a small block Pontiac on it, Not looking for the performance of a Holley. It was recommended I try out a AFB carb, the carb is a 3721SA off a 64 Corvette 327. I have on hand a 3649SA off a 64 GTO 389 and a 4242S off a 67 Firebird 400 and 4028SA off a chevyII 327, I am testing out for the best performance and throttle response.
Installing them on a 67 326, mildly built.
The 3721SA has great idle to part idle response.
the 4242S has great idle to part idle response.
the 3649Sa has good idle to part idle response.
the 4028SA which is a AVS has great idle to part idle response.
They are all 575cfm's and are decent I am wondering which would be the best mix for my 67 Pont. 326?
Which ever one floats your boat. Probably the 4028SA.
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Old 08-06-2012, 07:34 AM
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Welcome to the forum!
Any of your carbs would work if you can get them to run. Have you tested all of them?
The eddy is basically the same carb as the afb. Have you got a carter strip kit for fine tuning your afb's?
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Old 08-06-2012, 01:15 PM
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Tuning the AFB

You should download and print this :http://www.mymopar.com/downloads/carterafbtuning.pdf This also will apply to the Edelbrock Performer Carbs, also your Edelbrock 1405 has the same internal parts as the Carter Competition Series 9635S,the common Edelbrock 1406 with electric choke is jetted leaner in the primaries for emissions,one of the first things to try when tuning these Carbs is changing the "pump shot" see that section first in the tuning guide no internal disassembly needed.
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Old 08-06-2012, 05:37 PM
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Originally Posted by RWENUTS View Post
Welcome to the forum!
Any of your carbs would work if you can get them to run. Have you tested all of them?
The eddy is basically the same carb as the afb. Have you got a carter strip kit for fine tuning your afb's?
The Eddy is gone, I won't go back to them, I had nothing but issues with them 2 carbs in 10 years, Carb shop in Mo. says they aren't for pontiac's,.
They all run, I cleaned them in chem-dry and rebuilt them and grab idle mixture screws, they seem to run very well.
I have a Carter AFB strip kit from 1986, not an earlier one,
I like these :
4028SA cause I can fine tune the secondary butterfly.
the only thing with this one I'd have to go back to a manual choke or find a way to install a choke on the manifold or carb.

4242S is real sweet too, no bog, I just got to find a choke coil for it.

the 3721SA is real sweet too, no bog. it just needs a choke coil too.
these 2 I need to find an adapter plate or new air cleaner. they are 4-3/4" throat.
This is the 4028SA
This is the 4242S
This is the 3721SA

Last edited by raguza123; 08-06-2012 at 05:53 PM.
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Old 08-06-2012, 06:09 PM
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I built a pair like the 4028's for a dual quad I had years ago. My buddy gave me a big box of afb's and I matched rods, jets and boosters to make a pair. Biggest problem was keeping fuel pressure down to 5 psi and setting optimum float levels.
If you need an adaptor for the aircleaner there's some on ebay.
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Old 08-06-2012, 07:19 PM
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[QUOTE=raguza123;1580555]I decided to go back to Carter's and put something ment for a small block Pontiac on it,[QUOTE]

First off, there is no such thing as a big block or small block Pontiac. Your 326 is the same size, externally, as a 455. Now to my view on carburators. IMHO, The best carbs for street use are either the Carter Thermo-Quad or the Rochester Quadrajet. Both are have air valve secondaries and are easy to tune.

Bill
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Old 08-06-2012, 07:33 PM
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[quote=WDCreech;1580750][QUOTE=raguza123;1580555]I decided to go back to Carter's and put something ment for a small block Pontiac on it,
Quote:

First off, there is no such thing as a big block or small block Pontiac. Your 326 is the same size, externally, as a 455. Now to my view on carburators. IMHO, The best carbs for street use are either the Carter Thermo-Quad or the Rochester Quadrajet. Both are have air valve secondaries and are easy to tune.

Bill
use to run Q-jets, always had a problem with warpage and leaky throttle plates and I could never figure out how to tune them.
I've been working on edelbrocks and now Carters and have learned a lot about the function and how to rebuilt properly and what to look for in wear.
And most Pontiac's engine parts are interchangeable, you are right about it, there is no small or big block.
As far as a thermo quad, I wouldn't even bother it seems to be more complex, I am thinking of about maybe trying a Q-jet again.
But for now the Carter's will do, they aren't for the track or performance, then again I have a 326, not too much more I can do with it
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Old 08-08-2012, 11:08 AM
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I was wondering if the 4028SA would be able to install a choke on it, does anyone know how to?
Otherwise I'll have to box it up and shelve it.
I also have an old AFB 9635S on hand, it's been in a box awhile, my only issue is to fine tune it, not sure how but it's still stock I would assume.
The older Carter's I will have a problem finding an Air cleaner for them, I gonna have to go to swap meets to find one, I'll box them up and shelve them til I find one.
they all need a good cleaning.
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Old 08-08-2012, 12:09 PM
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You can put a manual choke on the 4028. You need to find or make a cable bracket like the eddy in this link. Air cleaner adaptors are found on ebay too.
Edelbrock 1405 performer Carburetor CORE 600 CFM SQ Bore Manual Choke 4 Barrel | eBay
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Old 08-08-2012, 01:31 PM
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I have that bracket from my first eddy, I had to trash cause it have a deep gouge on the bottom side. I have a lot of extra parts from the eddy left.
the Carter 9635s isn't any good, you thinking the AVS is the best fit?
I could drill out the base to fit a choke? or you don't recommend it.
I have an air cleaner adapter, it makes my air cleaner too high, it hits the hood, and I'd have to order a filter to lower it. I'd get a K & N then.
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Old 08-08-2012, 01:53 PM
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THe avs would work if you want to make the choke work. If the cleaner adaptor makes it sit to high you can find a dropped base air cleaner to give you room.
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Old 08-08-2012, 02:27 PM
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Where's a good place to look for a dropped base air cleaner? because that would work.
I'm getting a lot of slack from others who say I can't run a chevy carb on a pontiac.
Pontiac's are low rpm engines and chevies are high rpm engines.
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Old 08-08-2012, 04:48 PM
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What!! Pontiac's will scream just like a chevy when you build them right.
You can run any carb on any motor. Just need to do a little tuning.
That's like saying you can't put a chevy sb in a mustang or like one I had, a 455 pontiac in a 64 ford 1/2 ton.

Ebay is your freind for parts. Here's a drop base k/n type.
14" ROUND RED FLOW THRU WASHABLE AIR CLEANER DROP BASE LID 350 454 302 347 460 | eBay
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Old 08-08-2012, 05:17 PM
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I have a bunch of AFB's on the shelf about 4 and 1 AVS, they all need to be cleaned because they they run a little rough, I'm not gonna throw them out, because they don't put out the top end like a Q-jet, Plus I have a 326 it's no major muscle engine, the 4028 and 3721 are from 327 cu. in chevy engines the later is from a Corvette, but I like the AVS cause I can dail the secondary valve to open when I like it to. They were recommended by a friend. I'm working on the 4028 first, giving it a through cleaning, I feel it wasn't clean enough.
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