Slant Six Forum :: Carburetor theory

one would get both power and best mileage using dual, staged, 2 bbl carburetors. For mileage, dual because it evens out the mixture to the cylinders, staged . . . because it's staged.

guessing - and hoping for correction if necessary - that, with BBD for instance, one would need not to get just any old BBD, because some were made for V-8's and some for /6's (maybe even some for 4 cyls?).

I think I saw that the old slants came out with about 160 cfm with BBS or 1920

Am I thinking straight when I think the higher cfm carbs wouldn't be the best choice for either power or mileage in a /6 dual carb setup?

Some posts in another thread seem to indicate that a BBD isn't really even that good a carb. Is that the consensus?

In theory, thoughtfully-selected, properly-calibrated and properly-tuned twin staged 2bbls on a well-designed manifold would be a good setup for performance and economy. There's no such thing as 'best', too many variables.

No 4-cylinder BBDs. There were 6cyl and 8cyl BBDs with jetting, sizing and hookup differences. Theoretically they're noninterchangeable, but it's not difficult to get a V8 BBD to run well on a /6.

the BBD has an excellent track record on Chrysler applications.

Quote:

There were 6cyl and 8cyl BBDs with jetting, sizing and hookup differences. Theoretically they're noninterchangeable, but it's not difficult to get a V8 BBD to run well on a /6.

Lots of head scratching, I imagine.

Hey Dan do you have the sizes for the slant bbd jets and metering rods? Im having the problem of to much fuel and I cant lean out my carb any more. I might be guessing that the carb is incorrect(v-8 bbd). Isn't the bbd rated at 280 cfm? if its only 80 cfm more just that much makes a difference.

Author:	RossKinder [ Fri May 12, 2006 12:01 pm ]
Post subject:	Carburetor theory
Well, not deep theory, I'll just say "theoretically speaking." From what I've read - theoretically speaking - one would get both power and best mileage using dual, staged, 2 bbl carburetors. For mileage, dual because it evens out the mixture to the cylinders, staged . . . because it's staged. It would seem that this is getting a bit into margins. Therefore I'm guessing - and hoping for correction if necessary - that, with BBD for instance, one would need not to get just any old BBD, because some were made for V-8's and some for /6's (maybe even some for 4 cyls?). I think I saw that the old slants came out with about 160 cfm with BBS or 1920, while some BBD's are almost double that. Am I thinking straight when I think the higher cfm carbs wouldn't be the best choice for either power or mileage in a /6 dual carb setup? Some posts in another thread seem to indicate that a BBD isn't really even that good a carb. Is that the consensus?

Author:	SlantSixDan [ Fri May 12, 2006 1:37 pm ]
Post subject:	Re: Carburetor theory
Quote: one would get both power and best mileage using dual, staged, 2 bbl carburetors. For mileage, dual because it evens out the mixture to the cylinders, staged . . . because it's staged. In theory, thoughtfully-selected, properly-calibrated and properly-tuned twin staged 2bbls on a well-designed manifold would be a good setup for performance and economy. There's no such thing as 'best', too many variables. Quote: guessing - and hoping for correction if necessary - that, with BBD for instance, one would need not to get just any old BBD, because some were made for V-8's and some for /6's (maybe even some for 4 cyls?). No 4-cylinder BBDs. There were 6cyl and 8cyl BBDs with jetting, sizing and hookup differences. Theoretically they're noninterchangeable, but it's not difficult to get a V8 BBD to run well on a \6. Quote: I think I saw that the old slants came out with about 160 cfm with BBS or 1920 The 1920s and BBSs are roughly 200cfm carbs. Quote: Am I thinking straight when I think the higher cfm carbs wouldn't be the best choice for either power or mileage in a /6 dual carb setup? Yes. Quote: Some posts in another thread seem to indicate that a BBD isn't really even that good a carb. Is that the consensus? No. The BBDs Carter built for Chrysler are very good carburetors. The ones built for Jeep were troublesome, and certain individual carburetors have given trouble to certain individual owners, but the BBD has an excellent track record on Chrysler applications.

Author:	AndyZ [ Fri May 12, 2006 1:56 pm ]
Post subject:	Re: Carburetor theory
that makes sense as long as you dont open up the seconary too much

Author:	emsvitil [ Fri May 12, 2006 2:03 pm ]
Post subject:
Some of the best writeups on carbs i've found on the internet have been for motorcycle carbs..............

Author:	RossKinder [ Fri May 12, 2006 8:02 pm ]
Post subject:	Re: Carburetor theory
Quote: In theory, thoughtfully-selected, properly-calibrated and properly-tuned twin staged 2bbls on a well-designed manifold would be a good setup for performance and economy. There's no such thing as 'best', too many variables. Got it. Quote: No 4-cylinder BBDs. There were 6cyl and 8cyl BBDs with jetting, sizing and hookup differences. Theoretically they're noninterchangeable, but it's not difficult to get a V8 BBD to run well on a /6. Lots of head scratching, I imagine. Quote: the BBD has an excellent track record on Chrysler applications. Thanks for the theoretical information!

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Author:	SlantSixDan [ Fri May 12, 2006 8:39 pm ]
Post subject:	Re: Carburetor theory
Quote: Quote: There were 6cyl and 8cyl BBDs with jetting, sizing and hookup differences. Theoretically they're noninterchangeable, but it's not difficult to get a V8 BBD to run well on a /6. Lots of head scratching, I imagine. Naw, it's pretty simple and straightforward. Some of them are as easy as tweaking the choke lever for hookup compatibility. Others require a little more parts swapping or modification (e.g. closing up the holes in the throttle plates).

Author:	mopardemon71 [ Sat May 13, 2006 12:21 am ]
Post subject:
Hey Dan do you have the sizes for the slant bbd jets and metering rods? Im having the problem of to much fuel and I cant lean out my carb any more. I might be guessing that the carb is incorrect(v-8 bbd). Isn't the bbd rated at 280 cfm? if its only 80 cfm more just that much makes a difference.

Author:	SlantSixDan [ Sat May 13, 2006 7:38 am ]
Post subject:
Quote: Hey Dan do you have the sizes for the slant bbd jets and metering rods? Im having the problem of to much fuel and I cant lean out my carb any more. I might be guessing that the carb is incorrect(v-8 bbd). Isn't the bbd rated at 280 cfm? if its only 80 cfm more just that much makes a difference. I don't think you have a "carb too big" problem. Remember, people run 4bbls on street-driven slant-6s! You've got a "too much fuel" problem; sounds like your carb's got an internal problem or two. Try another!

Author:	RossKinder [ Sat May 13, 2006 9:57 am ]
Post subject:
Quote: Hey Dan do you have the sizes for the slant bbd jets and metering rods? Im having the problem of to much fuel and I cant lean out my carb any more. I might be guessing that the carb is incorrect(v-8 bbd). Isn't the bbd rated at 280 cfm? if its only 80 cfm more just that much makes a difference. http://www.tocmp.com/manuals/Carbs/Cart ... index.html Appears to show a staged at .098 and .083 and non-staged at either .089 or .092.

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