There are often threads on these forums as to "what is the best carb for my *****"? Or, "how large a carburetor can I use"? Generally, these are questions that have no absolute answers; as too many variables enter into making an informed suggestion. But AS A STARTING POINT, I have gleaned data from several original Carter documents, and combined it into a table. For the most part, the data is H.A.M.B. friendly, but a bit of the data is slightly newer, and thus would be considered off-topic. With respect to Ryan, I will not post the complete data here, rather post a link to my website, where all of the data may be viewed. The data is presented only as data. For those that wish to argue, you probably need to schedule a seance, as the newest data was done about 45 years ago. Probably most of the engineers making these recommendations have past. I knew many of them, and they, and their knowledge base, is sorely missed. And for those of you who have installed four (4) 950 CFM carbs on a 4' tunnel ram on a 265 Chevy, and it will idle so low you can count the fan revolutions, I am happy for you. I personally like to believe that engineers do things for a reason. So, here is the link: http://www.thecarburetorshop.com/Carter_aftermarket_4-barrel_carburetors.htm If there are specific questions about the carburetors, I will try to help. Jon.
Thanks for link - bottom line is that you need to still run the best carb for your motor - most will turn to the readily available Edelbrock Carter replacement
Thanks for compiling and posting the table, good info there, and on your website overall. I'm piecing together a 2x4 setup to go on a mildly hopped up '59 389 Pontiac. I have both an Edelbrock P22 and an Offenhauser 5029 manifold. I also have two #2767 '58 Pontiac AFBs in decent shape to work with. I have a pair of 3721 Chevy AFBs but I'd prefer to use the Pontiac carbs on my Pontiac engine if possible. Of course, there has been some previous tinkering and I found out immediately that the auxiliary air valve encountered interference when opened. I had a feeling that they switched locations of the secondary booster venturis side for side. I switched them and now the valve moves freely as it should however, I don't really know for certain that they are in the correct location or are even the correct boosters. So, I'm wondering if you can confirm the locations of the boosters by the numbers stamped on them. Driver's side primary - #297 Pass. side primary - 296 Driver's side secondary - 197 Pass. side secondary - 196 Any additional tips to help me get to a decent running starting point would be appreciated. Thanks.
The venturii, as listed are correct. On a Pontiac engine: The Pontiac 2767 might require a minor rod/jet change, perhaps not, much depends on the cam The Chevrolet 3721, to run right, would need virtually the entire carb to be replaced. Calibrations for Chevy are just plain totally different than for virtually everything else. Everything means idle jets, main jets, rods, springs, air bleeds, restrictors, bypasses, and especially the auxiliary air valves. The P22 will be the choice of all of your Chevrolet buddies, but the Offy will perform better on the Pontiac engine. For future reference on Carter AFB's, generally the primary clusters cannot be installed wrong; but the secondary clusters can be. Locate the brass insert with the tiny hole (air bleed) on the side of the secondary clusters. It faces toward the fender, or worded differently, the two face opposite of each other. Carter referred to pump side and choke side rather than driver and passenger as some folks drive on the wrong side of the road Jon.
Thanks Jon, glad to hear that my first choice of carburetors is workable. Between the two intake manifolds, I noticed that the carbs are farther apart and centered over the ports on the Offy and clustered in the center of the Edelbrock, obviously a little difference in the engineering approach. The Offy seems to have more plenum volume than the Edelbrock. My only beef with the Offy is the way they made the main casting with the small square pattern and then used adapter plates to accommodate the later AFB and Holley carburetors. Add in a heat rejecting carb spacer with gaskets it starts to look cobbled together but I guess whatever works, huh? Here’s pictures for comparison. (Ignore my messy workbench)
I will be drilling and tapping the boss for a conventional curb idle screw per the tips on your web page because now is the time, while the carbs are apart and on the bench. But, I can see where the Idle Air Screw could be helpful to get a good idle depending on how big the cam is. The internals of this engine are unknown but it was assembled and installed by racers who had little interest in leaving things stock. The engine is a ‘59 with a ‘57 Pontiac fuel injection at present (dormant for 40 years). Does the ‘1 turn open’ starting point still apply with the dual quads? Or should I close the valves and only open them if needed? Thanks again.
If you are modifying for the conventional idle, then turn the air screws all the way closed; and only use if required because of a wild cam. 1 turn on the mixture screws is still a good starting point, but might be slightly rich. As an unknown start-up, rich is better than lean And if you no longer want the '57 fuel injection unit, someone will no doubt want it, and probably pay for all the mods you are doing to the car! Some Chevy dude will want the 3721's as well, desirable units IF you have a Chevrolet engine. Not overly useful for any other make. The adapters DO look hokey (looks like you are missing a couple of screws), but the Pontiac spacing is worth it. Jon.
I have both a '57 and a '58 Pontiac F.I. and I hope sometime in the future to rebuild and install one of them. It's like catnip to a compulsive tinkerer, can't wait to dig into them. But, I have to focus on getting the poor old Pontiac running again before going off on any tangents. The Offy was missing a screw so I took one out to take to the hardware store to match up. I'm still carrying it around in my pocket. I finished going through the first 2767 AFB today. It had two different metering rods in it. A 16-406 and a 16-72. I have a couple of Carter strip kits. I put a couple of 16-544s in there for now. Can you suggest a pair of rods that will be close to stock. The jets are 120-160 primary and 120-229 secondary. No idea if they have been changed. Thanks again.
Ever wonder why when one of the 1957 or 1958 FI Pontiacs are on a TV auction, you hear the auctioneer "this car has amazingly low mileage"? There is a good reason. I have never personally owned one; however I had a good friend who bought a 1957 new. He used to buy coaster diaphragms BY THE DOZEN!!!!! and carried TWO with him in the glove box. But back to the dual quads: 2767s had rods 16-72. The only rod that is close enough to run without changing jetting would be 16-25. Don't even think about the 16-544 unless you change the jets; 16-544 would be WAAAAAAAAAAAAAY lean with standard jetting! Unfortunately, the strip kits contain rods with profiles designed for Chevrolet engines. The rods are really not very useful for Pontiac engines. Some extra Pontiac cores are quite useful as parts carburetors. If you cannot find Pontiac rods and have to use strip kit rods, then pick those that have the proper high vacuum dimension. These will be incredibly rich on WOT. As I have posted before, Chevrolet calibrations are just different than calibrations for other brands. Back in the day, there was no need for Carter to produce aftermarket parts for Pontiac, simply because Carter produced performance O.E. parts for Pontiac. Jon
Just put them back in until there are no parts left All joking aside, Carter carburetor school taught to group parts into their application. In other words, put all the choke parts together, the throttle shaft parts together, the float bowl parts together, etc. Jon
In my case all of the additional parts resulted in a hood clearance issue. I'm happily following along since I have a Pontiac with the offy manifold that is about ready to run.
If there is a hood clearance issue because of using BOTH the adapters and phenolic spacers, don't! Thermoplastics exist today that may be machined to replace the adapters, so now the adapter and the spacer is the same item. Jon.
Don't confuse the Edelbrock carb with a genuine Carter AFB even though they look close to the same on the outside, they are definately not, the Carter is a much better carb.
Funny that's what I've always done, I have baking pans that I put each subassembly in and work one subassembly at a time. I don't usually remove the throttle blades unless the shafts are loose and need attention. After working on these two AFBs, that had obviously been blasted in the past, I'm not a fan of media blasting carburetors, I'm rinsing that junk out of every nook and cranny.
I just split up a dual quad setup after I found the Carters were fairly specific (no #s here, will post from home) One was for a manual Vette and the other was a 60s Caddy with AC. I am sure their are folks out there looking. Thanks for posting all the Carter info!
Thanks! I think that having heat isolation is a good plan. I don't have any heat isolators and still had to modify the hood bracing with only the adapters. Sounds like I can have both without an additional clearance issue.
There are some good heat isolating spacers out there right now. I bought these off of eBay. I like that the brown AFB pattern spacers are only AFB bolt pattern but I wish that they made the black ones with all eight holes like the generic base gaskets do. The 4 bbl versions are .5" thick and the 2 bbl version is .250". I put them on everything, but then I don't have any hood clearance problems.
The brown phenolic spacers came from Dashman’s Hot Rod and Speed Parts, they are nice. They seem to have a lot of different choices, thick or thin, for a number of popular carburetors, seems to have other stuff too. He may be a HAMBer. IDK. I have no interest in this company just passing along the info.
The Jalopy Journal
