Last weekend I bought two Carter AFB carbs on a Offenhauser 5253 low rise intake. The rear carb number is 3361s abd the front is 3804s. After researching the numbers they are off of a 425 hp 409. Not sure on the internal condition, the rear carb is missing the outer choke housing and the front has stripped out throttle blade holes. The guy I bought them from said his buddy only used the rear carb for his 355. I'm building a 283 for a 29 model A truck. I have $200 into the carbs and intake and I'm not familiar with Carters but like how they look. I'm wondering if they work on my motor or sell them to a guy building a numbers matching 409.
I had two AFBs on my 327 I had in a '60 vette---really liked the way they performed. If I had your problem(??) tho, I'd advertise them for a 409 guy and buy two new Edelbrocks for the intake. That way you don't have to go through the old ones. Just my 2 cents.
They are definitely worth some big bucks to a 409 restorer. Way too much carb for a 283 but they would probably work on your motor as long as the original counterweighted air valves are still in place over the rear barrels on both carbs. They look cool but a single 4 bbl will out perform them on a 283.
Carter used to make matched pairs of 400 CFM carbs for 2X4 set ups, still a bit big for most engines.
I would've thought they'd have both been 3804s. Do they have special throttle plates for the progressive linkage? It'd be a factory add-on plate with a few holes at the top.
I got a pair of ASFbs that I am setting up for a 2x4 low rise offy on my 355. They will work fine on your little motor. You will have to fiddle with the jetting and the weights on the secondaries. The secondaries are vacumm over mechanical, so even though the secondaries come open machanically the flapper that lets the iar in is dependent on engine vacumm not enough vacumm and you don't actually pull the secondaires open. Once you are dialled you will be fine. You do want to run on the rear and the front will be your secondary carb with that intake.
The numbers are correct for the later 409; however, the positions listed are incorrect. The 3361s (without choke) would be the front, and the 3804s (with choke) would be the rear. These are 625 CFM carbs; lots of carb for a 283. I believe you would be much happier with two 400 CFM units. The Carter part numbers are either a 9400s or 9410. These carbs may be matched or mixed, as the 9410s is simply a 9400s with an EGR port which may be plugged. Jon.
The carbs that came from a factory car with two and progressive linkage was never drilled for a choke. The primary carb had the choke. That is one reason these are so expensive.
The front/secondary carb also did not have idle air adjustment screws if it was for the dual carb setup.
Agree - sell those to a restorer and put two new Eds on your 283". On mini-motors, progressive linkage and vacuum secondaries are your friend. It's doubtful if a street 283" will ever pull open the secondaries very much. The math says it won't suck 600 CFM, much less 1200. The 600 CFM are usually the loss-leader carbs my local speed retailer advertises. Don't be afraid of those advertised as "re-manufactured" Those I've bought didn't show any sign of ever having been installed. Also, the electric choke pulls off so quickly, you can even leave them both adjusted as is and usually works fine. Progressive linkage is worth at least a couple of MPG around town. jack vines
I had the numbers mixed up. What I found on the 409 sites is that the dual quads are 500 cfm each and the single quads are 650 cfm. It seems that a lot of people use dual 600's on a 350 without a problem on a midly build motor. I guess it just depends on how good of a tuner you are. My original plan was to use three Rochesters. I am also wondering about the rpm range of the intake. Can't find much info other then it is a 360 design with tuned runners. Would a C26 Edelbrock work better on a smaller engine since its a dual plane? I'm using ported 416 305 castings so flow should be better then the stockers.
she's real fine my 409 three two's and a four speed...hear er' whine whine whine.... restorers don't pay much for after market.....now if you had a Nascar single four..$$$....that's what one of buddie's '09 ran best with...
As far as I can find, Carter did NOT publish actual CFM ratings for the 3361s/3362s/3804s; HOWEVER, the primary throttle bores, secondary throttle bores, primary venturii, and secondary venturii are exactly the same size as an O.E. carburetor that did have a published 625 CFM. The single quad 409 carbs are 1/16 larger and I would agree with the 650 rating; although again, I can find no published data in the flow tests from Carter. Different from popular belief; MOST O.E. carbs had no published rating on CFM until the 1970's. Carter did flow their O.E. carbs, and I have the Carter files showing the results of the flow tests; but these tests were conducted to determine A/F ratio at different loads; NOT CFM. From the parameters tested, impossible to determine CFM from the tests. As to the post that a single four would outperform duals on a 283: while I have no scientific evidence to dispute this, SEVERAL 283 customers have been delighted with dual 9400's. It is certainly easier to make a single quad perform well since one only has to deal with a single carb. Having said the above, a historical note: When Mr. Granatelli wanted dual quads for the Studebaker Avanti R4 engine, he did not want a sufficient quantity for Carter to produce different tooling. The Carter 3810s/3811s used on the R4 304 CID were 3361s/3804s basically with a change to Studebaker linkage and different jets/rods. The Carter AFB carburetors, because of the metering rod technology, are quite flexible. As for the NASCAR version mentioned above by stillrunners, GOOD LUCK on ever finding the 3593s. I have yet to see one. Basically the same castings as the Pontiac 3596s which I have seen (one). Both were 750 CFM. Jon.
Who'd ague with the carbking? Not me. Yes, with progressive linkage, they can be made to drive out nicely. As previously mentioned, they can't "over-carburete" as the secondaries won't open if the demand isn't there. As someone who has fought several of these battles, I no longer even look at a carb unless there's a wideband O2 sensor in the exhaust. You don't know how much you don't know until you can see air/fuel ratio in real time. Yes, the 305" Studebaker R4 did use two 625 CFM Carters. Even with progressive throttle linkage, it was an 8-12 MPG. jack vines
Replacement parts are available,and parts carbs are cheap.I suggest downloading "Servicing the carter aluminum four barrel carburetor" at carburetor parts .com They are easily rejetted to suit your needs. .
It won't make any difference to a restorer, but 'back in day', about as many or probably even more "409 dual quad-spec" AFB carb sets were sold "over the counter" then were ever installed on 'assembly-line built 409 Chevy cars, for use on all kinds of home-brew and otherwise, non-stock dual quad set-ups. I recall that after Chevy discontinued the hy-po 409's , that back around 1965, '66 or '67, that Gratiot Auto Supply in Detroit - to name just one vender - ran magazine ads offering brand new, factory-surplus "dual-quad 409-spec carbs" in matched sets for something like either 29 or 49 dollars a pair!!!
Jetting on the new Eddy 500's are for the 2x4 setup. If you get 600's, you will have to spend a lot to get the jets and needles in proportion to the ratio of the 500's. Been there, done that. I used my wide band gauge to find out how far off I was with the seat of the pants tuning on the 2x4 setup. I used a friends 500s for a little test session and they are right on the money. But, you CAN'T just use the jet and needle numbers from the 500s in the 600s. Original AFB used 3 step needles in a lot of applications, 2 step is all that is available now.
Jon, Are the carbs 625 CFM each ? Would it be too little/too much for a stroked 348/448 running street cam with big intake valves (2.19"), 9.5:1 compression 5500-6000rpm ?
What means 348/448??? Is that 348 before stroking and 448 after? As I stated above, Carter did not publish flow ratings on the 409 2x4 carbs, but the throttle bore and venturii are identical to a published 625. I am comfortable calling them 625's. If this is a 448, I think you would be happier SELLING the factory 409 2x4 set to a restorer, and replacing them with two 4759s 625's, and run solid linkage. Choke on BOTH, idle on BOTH. Easier than converting the 3361s to a complete carburetor. If you want to know the reason for replacing two 625's with two different 625's, CALL. If it is a 348, then run them with progressive linkage. The perormance 348's came with a single 675 CFM carb. And before I receive a bunch of "hate" posts on the choke on both for a street driven vehicle, TRY IT: IT WORKS! A working choke will actually IMPROVE performance on the primary side, and will not impair performance at WOT unless the carburetor is too small. It works on certain race conditions as well; this we have proved with the roundy roundy folks on dirt tracks. Jon
Jon is correct as always, I run chokes on both carters on my 383 mopar non progressive linkage and it works flawlessly in all weather
You would be WAAAAY better off with 2 Carter WCFB’s like the 245hp and 270hp 283 used and set the same with progressive linkage. You could cover the costs with what you have unless you’re wanting originals of them. All you need is 2 of the same year and number and just turn the front choke heater so it never comes on. This would be fairly easy to do for a Chevrolet since there were so many and used for many years. Here’s a photo with 2WCFB’s with Harley Davidson air cleaners on a stock Ford Y-block so you get the idea. Been on 7 years with very very few adjustments.
I run a choke only on primary carb of dual Carter WCFB intake on a 283, engine idles on both carbs and uses progressive linkage. Starts and runs great, no bog when pinning the go pedal to the floor, with a nice bump in power when the secondary carb is activated.
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