Was reading this old thread and thought I would ask https://www.jalopyjournal.com/forum/threads/carter-dual-quads.818648/ I have an old Edelbrock 2 x 4 Ford FE intake and 2 400 cfm AFBs Am building a .040 over 390 with a 428 crank ( 418 ci ) Only street driving for weekends, car shows, etc ... not worried about power Are the carbs going to be too small ?? Ricky.
Not really, it doesn't quite work like that, because of the way that carbs are rated, and the reduced velocity, or pressure drop, from dual carbs vs one. It's probably more like ~600 cfm.
For this type of driving, you will probably be alright, assuming you take the time to dial in the carbs. For normal driving, probably too small. Personal experience: My shop truck has a 390 with 390GT heads and cam, and an Offenhauser 2x4. The carbs are genuine Carter AFB 625 CFM. Linkage is solid (both run all of the time). Runs like a scalded dog, and I won't post the fuel mileage, as the Holley dudes won't believe it anyway. Jon
Again, you'll be fine. Should run great around town. Just be sure to synchronize them. Either by a synchronizing tool, OR by "carefully" setting the primary throttle blades using a drill bit to make sure that they are the same amount of open. Use the stock setting as a starting point. A synchronizer tool is best though. Two and four gauge motorcycle tools are available. Some will say that you don't need to have both flowing the same. IF, you want the engine to run well...you do ! Mike
I have someone interested in the 400 cfm carbs .... would like a pair like Carbking's In my youth, built up 15 or so Dodge/Plymouths and used various AFBs on them all except a few Holleys ..................................... Ed. F262 intake 1st carb The secondary linkage sticks out farther than the second carb 2nd carb Ricky.
winr - don't give the 400's away; they are very much in demand, and command prices some folks on this forum would never believe. The carbs on my 390 are "marriages". I started with the Carter 4759s Comp Series 625 CFM strictly for the castings an manual chokes. But these, like all the Carter aftermarket AFB's are calibrated for Chevrolet, and TOTALLY unsuitable as is for almost anything else. So the next step was to do an inventory search, and find two MATCHING Carter AFB's for 430 Lincoln engines in my inventory for "donor" carbs. Disassembled everthing, and removed AND REPLACED primary and secondary clusters, primary and secondary jets, step-up springs, and most importantly the auxiliary air valves from the Lincoln carbs to the Comp Series carbs. Also replaced the throttle arms, as I wanted the "factory look". Put it all together, and did some testing. Had to machine new step-up rods, as the Lincoln rods were not absolutely perfect (they would have been good enough for most folks, but the mid-range was a bit rich). Did the math, and got the new rods right enough to satisfy me the first time. I mentioned this on another forum once, and one dude laughed at me; stating that a carburetor does not know what brand of engine it is feeding, it simply feeds a group of holes with vacuum. He was correct as far as he went, but each engine has a different vacuum profile graphed against RPM. For best performance, the carburetor tuner should listen to the engine. Jon.
Found a few pair of AFBs for sale ..... 2 x 9625 SA .... 2 x 9605S ... 2 x 9635 SA ....2 x 9635 S ....4 x 9637 S ..... would any pair of those work perhaps ?? ... or do you build carbs for folks Carbking ?? ..... .............................................................................................................................................................................. I also has an old Ford FE Edelbrock 3 duece intake and 4 WW Strombergs off of 318 poly truck engines Ricky.
The 9637s could be made to work with some tuning and parts replacement. The 9625sa could probably be made to work with a LOT of tuning and parts replacement. Same can be said for the 9635s. All of the above are electric choke. Personally prefer manual choke on dual quads. You are probably going to need some donor carbs for the 9625sa or the 9635s. You will probably need to have some custom step-up rods (or possibly some donor carbs) for all of the above. Run from the 9605s and the 9635sa. I no longer build carbs (too busy with the manufacture of carb rebuilding kits). Jon.
When selecting aftermarket carbs; think like an engineer. Is there any history? Unfortunately, Ford didn't purchase Carter AFB's for their dual quads or single quads after about 1960 (too bad, if they had, we might have averted the 1973 oil embargo ). But Carter did produce dual quad AFB's for both Pontiac and Chrysler. And both have fuel calibration curves extremely similar to Ford. No, you don't have to run out and buy expensive factory dual quad Chrysler or Pontiac carbs (although I have some of the Pontiacs available ). But acquire the specification sheets (jets, rods, springs, air bleeds, bypasses, restrictors, auxiliary air valves, etc.) and use these calibrations to modify whatever you start with as a base-line for the Ford engine. Jon
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