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#1
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Does anyone know where I can get the CFM ratings for carter AFB`s and carter AVS 4brl carbs? ......Also what is your thoughts between both?, do either have a performance/ milage edge and why?
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#2
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Good questions there rustytoolss.
For the most part, today, you can find the AFB & AVS in the 600 cfm ratings most. They booth also came in a 750 rating. AFB's also come in a 500 cfm version as well. Performance wise there very similiar. With the AVS, you have the spring loaded door to tune for MPG's or extra ZIP. The problem with the door is it as not an areodynamic door like the T-Q. Its not a big thing at all. The AFB has the counterweighted door. This can be made to open up quicker very easy. It just requires a little grinding of the counter weght. It CAN be made to open slower, but it would require drilling and the adding of heavy metal in the hole you made. I don't think its worth the effort there. They can give good MPG's. Have gotten 20mpg's with my '79 Dodge Magnum 360. With an MSD, Dual exhaust and an aircleaner from a '73 Challenger. This was done with the emsions AFB rated at 625. Tell us the throttle bore size, we'll come back with a rateing. |
#3
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Hi rumblefish360,
I just got a 750 avs carter off a '71 440 truck for my stock '65 383 sport fury, 3.23, 9.2 compression. I had a two barrel and got a junkyard four barrel manifold from a van. Any thoughts on this combo? I really appreciate any advice, this is my first big modification to the car. |
#4
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B.B.Babe;
In My Opion, the carb is to big. But that dosn't mean it won't work. You should get a real top end increase with it. Rejet the carb as needed on the primarys first. Thats where you'll find the most gain. The carb can use AFB rods & jets. You'll need to change the rod covers over to the AFB "flat" type covers as the AVS's are bubbled for the 3 step rod. This conversion is a no brainer. An easy swap. Rod cover tops should be easy to get from Carter (Federal mogal) or Edelbrock. You might have to readjust the tension on the air door a little tighter/loser. The 440 pulls more air and so its set up for it. Its a minor adjustment to do after the primarys. Have fun, good luck. |
#5
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Thanks for the advice!
I thought the carb was too big, but I wanted to have a carb I could use after more modifications. I heard it is easy to adjust for over carburation because of the spring door. Do you know how big the primaries are compared to the smaller avs? Furthermore, instead of replacing the three step rods, can't I just replace the jets? Are not the three step better than the two step because they are more precise? |
#6
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THE 750 CFM WILL HAVE THE 1-11/16" PRIMARY AND SECONDARY BUTTERFLIES.
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#7
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Well, Yes, the 3 step rods are more precise. Do you have full understanding on when the middle step is used and comes in? And @ what vac. reading it happens. The springs will tell you the point @ where they begin to overcome the vacum force.
Yes, the jets are the same. Its harder to tune "Jets than rods". Get the jetting right then fine tune with the rods. The spring covers are cheaper than dirt. With the new covers on, you'll have a wide selection of rods to work with in addition to the jets. It's just a pain in the A$$ to take the cover of everytime to get to the jets to make a change. 2 screws semi off to swing the plates to the side for a rod change vs. all the bolts and pins that hold the linkage on. (dripping gas to) And yes to the spring doors abilty to tune is good. But not the only factor. Primarys first. The spring loaded door is for the secondarys. Tuneing that door will prevent sluggish acceleration. Not part throttle acceleration. Like causal driving. These specs come out off Super tuning & modifying Carter Carb's By Dave Emanuel. The should be compareable if not exact to the AVS. Carb._________Venturi dia._________Bore dia. CFM__________Pri.____Sec._______Pri._____Sec. 750 ................1 7/16.....1 9/16 ......1 11/16....1 11/16 625.................1 3/16.....1 9/16.......1 7/16......1 11/16 575.................1 1/4.......1 9/16.......1 9/16......1 11/16 500.................1 3/16.....1 1/4.........1 7/16 .....1 11/16 400 ................1 1/8.......1 1/4.........1 7/16......1 7/16 That 750 will serve you well. Have fun. |
#8
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Thanks for the info Rumblefish360.
Very helpful, you make a good point about the ease of changing rods vs. jets. |
#9
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Rumblefish, thanks for the cfm info for the carter carbs.
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