I read some things in here about the undesirability of refurbed carbs, and I'm apparently finding reasons to agree.

I've been asking this and that here about 2 bbl carbs as a replacement for my refurb BBS that seems to have outside parts that don't work smoothly. Who knows what's going on inside.

From statements by folks here I've concluded that a 2 bbl should be staged if you want any economy. But I haven't had much luck in learning how to acquire staged BBD's.

1. Is there a trick to finding these?
2. Do I need to look somewhere besides the BBD?

Thanks.

There are no staged BBDs that's why you can't find any. It's kind of like asking for cold fusion at this point.

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Joshua

By far the most common staged two barrel carb you will find will be the Motorcraft/Holley 5200 carb. It was installed on large numbers of FOrd/Mercury four cylinder engines in the 70s and 80s. It was also installed on Mopar four bangers in the early 80s, but is usually computer controlled. It flows 280 CFM, the same as a BBD, so it should give enough flow for a stock motor, but it looks rather small and may not work on a modified engine.

After that, you are pretty much looking for Weber carbs. These will all be either universdal fit carbs or come from some kind of European car.

Holley did make a staged two barrel carb briefly in the 80s. It was the Holley 2305. If you can find one of these at an affordable price, get it. It flows either 350 or 500 CFM and shares most parts with the Holley 4160, meaning it is very tuneable. But it is a Holley, and thereforer prone to leaks and a pisser to get tuned (and keep tuned). That last bit is my personal opinion.

Check this out:

http://www.225.ca/tech/jstk001.htm

What ever you decide, you will have to run a carb adapter and fabricarte the throttle and kickdown linkages.

Reed,

I have since updated that carb article I originally wrote way back in the mid '90s. My position on Weber DCOE types has changed a bit. They can be made to work very well and provide very good torque and economy, but it usually takes a considerable amount of tuning to do so. Due to the complexity and expense they don't get my recommendation very often. For a lot of folks even adapting a staged 2bbl into an automatic transmission equipped vehicle ends up being too complex.

The Holley/Weber 5200 came on lots of GM 4 cylinders too. Vegas and Monzas used them. Of course every Mopar engined carbureted K-car used them, but they are a feedback carb.

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Joshua

I think you mean it was computer controlled on Mopars? No problem there. Very tuneable but...? Stick shift so no sweat on the kick down, right? Thanks

It does sort of seem like that could affect the situation a little bit.

Hmmm. If dyou were handy with machine tools (or know someone who was) you could cut the throttle shaft on a BBD in half and rig a bolt on staged throttle linkage. If you were really bored that is.

I'm VERY handy with tools, etc. The problem is finding tech data or drawings or descriptions or whatever to show me where I'm going. Carburetors are a few levels below the bottom of my experience list. They've always seemed demon possessed to me - ready to head to the underworld at the drop of a hat.

I know tools and machines, but not carburetion - too many unknowns. Bored? I'd have to know something to be bored about. Thanks.

Well, here is how you could do it.

(1) find a BBD that you are willing to mess with

(2) completey disassemble it

(3) remove the four screws holding the throttle shaft to the throttle plates and remove the shaft

Now comes the tricky part.

(4) you will see that the throttle shaft passes through a bushing on the outer edges of the throttle bore and also passes through the bottom casting piece of the carb in the middle. THe middle section will have to be machined or modified to accept a bushing or other mount for the two throttle shafts you will be creating.

(5) Measure the throttle shaft carefully and cut it right in the middle of the center section that passes throgh the carb.

(6) The stock throttle linkage will now operate the left throttle bore, but you will have to fabricate some kind of system to translate the movement of the throttle linkage to the right throttle bore, with some means of delaying the actuation of the right throttle bore. My idea would be a double bell crank system with a slotted cam on the right side. It would also be easier to get the throttle shaft from another BBD and cut it to form the right hand throttle shaft. This would be better because you wouldn't have to lengthen the original shaft piece or worry about how to attach a linkage to it.

(7) Once you get the throttle working right, you then have to worry about the internals. The BBD is designed to have synchronous accelerator pump shots and metering rod movement, as well as a shared fuel bowl for each bore. The accelerator pump hole could be blocked and the metering rode removed on the right side, but the main jet for the right bore feed could be a problem. I don't know enough about carbs to figure out a solution, except maybe a custom metering rod on the left bore with a fatter main jet and a small or blocked off jet on the right side. Or maybe a custom metering rod on the right side could be made to block all fuel flow through the right jet until the throttle was opened.

The choke and fast idle linkage could be kept stock, but the vacuum advance port feeds off of the right throttle bore, so that may be a problem. Otherwise, this sounds like it could be done. I think the hardest part would be figuring out how to make the internals work, followed closely by how to make the center section of the shaft be supported and not bind.

A very interesting project. I would love to see it be done! But it would be much simpler just to buy a Weber.

I started doing that to a holley 4412 (500cfm) many years ago. Never completed it. I drilled holes in the side of the primary and secondary barrels and used them for vacuum port to operate a vacuum secondary pot from a 4 bbl carb. I need to fab a mechanical failsafe linkage to close the secondary throttle. The carb is still sitting on the shelf, so maybe someday, in my spare time

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Interesting to say the least. Thanks.

Google found nothing but a manual on the 5210, somewhat more on the 5200. By digging around I found an apparent connection between the number 5200 and the letters DGV, DGAV and DGEV. I'll be looking for more on this, but if you can enlighten me as to whether these are all various forms of the 5200 it will help. Thanks.

The dgv, dgav, and so on is weber´s name of the carb holley made copys of.
They are basically the same.

Thanks

Holley you are talking about do exist for 5220 progressive carb and another one that looks similar but not is 6520 computer controlled carb.

Found on many old 2.2L in K-cars and older caravans. Tulip (87 caravan) have 5220. Omni and Horizon too. I have another that is mechanical secondary, look for that one mechanical secondary 5220. Others is vaccum operated secondary.

If you see a big can with 4 philips screws linking to the secondary butterfly, then that's vaccum secondary on either 5220/6520.

Cheers, Wizard