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Veteran
Posts: 269
 
Location: Chesterfield, Virginia | I would like to find the CFM size of these two 59 Carter AFB carbs.#1 is AFB 2794s,Throttle Bore---primary size is 1-7/16",secondary size is 1-9/16".Main Venturi----primary size is 1-3/16 & secondary is 1-5/16. THE second carb is Carter AFB #2790s,Throttle bore ---Primary size is also 1-7/16" & Secondary size is also 1-9/16". The Main Venturi Primary is 1-1/16" & the Secondary size is 1-1/4. I've had no luck so far finding the size or CFM of these carbs .Thanks ahead for any info.  |
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Expert
Posts: 3778
  
Location: NorCal |
You will hear lots of AFB CFM ratings bandied about on the WWW but all of them are just guesses. The simple fact is that Carter never published CFM ratings for OEM carbs. |
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Veteran
Posts: 269
Location: Chesterfield, Virginia | I did find the Cfm of 1959 ABF #2790s carb is 465 CFM. The info for the other carb must be somewhere . |
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Expert
Posts: 3778
Location: NorCal |
Where'd that info come from? |
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Veteran
Posts: 269
Location: Chesterfield, Virginia | I ran across it on a carb web site last night. |
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Veteran
Posts: 269
Location: Chesterfield, Virginia | Type in "Carter afb carburetor #2790s rating" on Google. |
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Expert
Posts: 1506
Location: Colo Spgs | Hola Yo'al
I too typed in the "Carter afb carburetor #2790s rating" using Google and read what seems as a bunch of Connector Guessing ( with Rose Coloured Glasses ). Some answers are
for only one Carburetor and some are with a total CFM of The Pair.
It says nothing of why all user's dropped the dual carb set-up and went to only one carb.
The 465 CFM is equal to what a single carb 440 or 383 was using in 1966.
Rodger & Gabby
COS |
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Expert
Posts: 2312
Location: Arizona | I'm more familiar with Quadrajets. All the info on them I've seen suggests the same basic carb layout ranged from around 500 cfm up to around 800 cfm. There's only so much you can vary the cfm with the physical layout you start with. Since the engine is at it's most basic an air pump a given sized engine at a particular rpm can only pump a certain amount of air. It would seem to follow that at some point you simply have exhausted the ability of an engine to use a "bigger" carburetor. If you do things to raise the redline you could logically use a bigger carb because at a higher speed it's going to pump more air. I would think a dual carb setup on a 400ish cube engine with a 5500 redline would be hard pressed to flow more then 800 to 1000 cfm. Which means each carb only needs to flow 400 to 500. Since one carb can flow 800 it one has to ask at what point the complexities of the dual carbs outweigh the limitations. With the cross rams you got the benefit of the rams so a dual carb setup has that extra benefit. With a dual carb on a central manifold it would seem like the result starts to become questionable for anything under 400+ inches and less then 6000 rpm redlines. Just my mental doodling. Might be why tri-power worked pretty well, sort of a sweet spot. |
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Expert
Posts: 3778
Location: NorCal |
I repeat, Carter never published CFM ratings for any of the OEM A series carbs (AFB, AVS). The only time actual CFM ratings were published is if an OEM carb hit the aftermarket to be sold as a universal carb. (like the 3705, 3861, et al) |
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Elite Veteran
Posts: 888
Location: Peoples Republic of Oregon | The best you can do with oem carbs is a simple comparison of throttle bores and venturi to a similar style aftermarket version.
Don't expect an exact match. |
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Expert 5K+
Posts: 8443
Location: Perth Australia | Not to do with the carby, but to those of us that dont know latin and always wondered what "ET AL" meant, I just looked it up
n. abbreviation for the Latin phrase et alii meaning "and others." This is commonly used in shortening the name of a case, as in "Pat Murgatroyd v. Sally Sherman, et al."
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Carb CFM info needed.
