Allcoupedup

I bought this carter AFB off of EBAY to fool around with before I touched my original carb. My carter books say ther there should be four metering jets but this carb hasonly two.

What gives?
Anyone recognize this carb? The date code is D3.

This carb had a bunch of sand in it and is pretty junked up inside. Is this thing even going to work when I clean it up? All of the sharfts and rotating parts operate smoothly.


allcoupedup


[Modified by Allcoupedup, 12:46 PM 2/25/2003]

SWCDuke

Boy, that thing is a mess!!! With the amount of corrosion/erosion in the pump well I don't think it's useful for more than a training aid. If the small air bleeds and idle jets in the venturi clusters and idle/off idle emulsion passages in the main body are severely corroded or clogged I don't think it will ever work right.

We'll need ClemZ to tell us the application for the 3805S, but there should be four jets, or at least threaded holes for four.

The primaries are in the bowl "alcove" between the primary and secondary venturies. The secondaries are near the back of each bowl along the inside wall, just to the rear of a metal baffle about 3/4s the way back. The baffles are held in place by "rails" that are part of the main bowl casting. I think I see the remants of the rusted baffle, but I'm not sure. You may have to use a dental pick to dig through the crud, but the secondary jets should be there or at least their mounting locations in the event they have been removed.

Duke

Allcoupedup

Duke,
After dipping the carb the model is actually 3503SA. I did find the secondary jets but they were hidden. I picked this carb because the fuel inlet and airhorn would bolt in place of my original AFB.


The butterflies and the main surfaces cleaned up nicely but the bowls are still in bad shape.

Can anyone recommend a method to attempt to remove some of the corrosion?

Thanks
allcoupedup

SWCDuke

That's definitely a different location for the secondary jets than on any of the AFB models used on Corvettes.

Duke

clem zahrobsky

AFB #3503 is a 1963 buick 325 HP 401 CI carb. bead blasting is the best way to remove the corrosion but the beads are a bitch to get out of the holes. :chevy

Allcoupedup

If I assume the carb is stock for a 401CI (stock jets and rods) is this thing going to run too rich for my 327/300? My intent is to use this as a back-up carb. The reason I ask is because I cannot get the jets out and stripped one of them pretty good trying.

Do the aluminum casting and the bronze jets bond over time? I soaked it in liquid wrench for a few days with no success? Any tips for getting jets out (any tips for removing stripped jets)?

Thanks for the info
Allcoupedup

clem zahrobsky

the jetting should work as the jetting has more to do with air flow thru the carb than displacement. BBC and SBC use the same jetting as long as the carb is not too large for the engine. once the aluminum corrodes it is almost impossible to get the jets out short of machining and retapping.

Allcoupedup

Duke/Clem- you guys are the best. Thanks for the information.
allcoupedup :thumbs:

SWCDuke

At idle and low speed/low load operation, fuel is metered based on manifold vacuum and each carb has to be tuned to the specific displacement and vacuum characteristics (valve timing) of a particular engine. The idle jets and air bleeds on an AFB that determiine idle/off idle fuel flow are part of the main verturi cluster, but some of the main body geometry comes into play, too.

As Clem said, once the system is operating on the main system, fuel flow is determined by air volume flow through the venturi and fuel flow is adjusted by tweaking the main jets and main air bleeds, so the jets and main air bleeds basically independent of displacement.

One of the trickiest carburetor tuning issues is the transition from the idle system to the main system and this is where the main body geometry comes into play in the form of the size and shapes of the off-idle transfer slots in the main throttle bore. This is otherwise known as "black magic" and how well it is applied will have a lot to do with the driveability of a particular engine configuration.

I have my doubts whether that carb will ever be serviceable, but you will learn a lot working with it.

LONG LIVE THE AFB - the simplest, most reliable four barrel carb on the planet!!!

Duke

Allcoupedup

Well, it's all back together. It cleaned up fairly well given the fact that all I threw at it was a dremel, a few carb cleaner dips, and some compressed air. I sort of reamed the pump cylinder with a small wire brush on the dremel and most of the crud came off. I'm a bit worried about the check valve though since I can't get that off either.


If it works or doesn't work I know understand the basic concepts of carburetors. I also learned that women do not like carb cleaner smell in the house!
Thanks,
Allcoupedup


[Modified by Allcoupedup, 4:12 AM 3/3/2003]