carter carbs afb/wcfb

[Stephen R.]

I have a 59 with a 283 that originally had an AFB on it. I decided to change that to a WCFB. I have both carbs and both were just rebuilt, figured I might as well do both at the same time. I have two questions. The original AFB carb sat on top of what appears to be an aluminum spacer appx 3/4" thick. So it's intake/ spacer/ carb ( all of the necessary gaskets are also installed ). I've been told that the spacer is not necessary. Is that correct? I thought it was a type of heat sink to dissipate the heat from the intake. Also with the spacer in place, the 4 studs holding the carb on appear to be really short and only hold the carb on with a few threads.

My second question deals with the idle adjustments. On the AFB there are two screw/idle adjustments, one that sits on the choke cam which is the fast idle and the other is located behind that which I assume is the normal idle. The WCFB that I have has only one screw/idle adjustment (although the book that I have shows 2) and that one idle screw sits on the choke cam. My problem is that when the engine is up to operating temp, I can't get the idle below 950 rpms and that's with manually pushing the linkage as far forward as I can. The engine normally sits at about 1000/1050 rpms. The choke is fully off and the one idle adjustement screw doesn't even touch the cam. Is there an adjustment screw that I'm missing? Were there WCFB's that have only one idle adjustment? How can I get the rpms down to something more reasonable? I could live with700/800 rpms if I could get there without haveing to mash the linkage forward. Would adjusting the mixture screws affect the rpms? I really don't want to play with the mixture adjustment screws unless I absolutely have to. Thanks for any info.

[William C.]

Re: carter carbs afb/wcfb

One thing you need to start with is what is the intake manifold you are using? The AFB and Wcfb use a different throttle bore size in the intake and a wcfb on a AFB intake will have air leaks. After that, what is the part number (off the foil tab) on the wcfb and for that matter (off the pass side front mounting boss) the part number of the AFB? Most chevy WCFB's used two adjustment screws, onr ofr fast idle and one for normal idle like the AFB, so knowing what carbs we are looking at might be a big help.

[Stephen R.]

Re: carter carbs afb/wcfb

Well that's my first problem. I didn't know that the AFB/WCFB's used different intakes. I wanted to use the WCFB since it's more appropriate for my car. Imay go back to running the AFB. Here are some numbers. I have two intake manifolds. the one on the car is #3844459/GM1/A184 1, the one in the basement is #3746829/GM5/F40. The carbs are (there are no tangs on either carb)

AFB: 2 (on the top)
6 1518 (top)
0 1552 (bottom)
3460 S K 2 (below fuel line)

WCFB:
6-1586 (top)
0-1465 (bottom)
The AFB sat and ran on the #3844459 intake for 35 years and ran well. I put the WCFB on that manifold Tuesday and it also ran well but again the idle would not drop below 950. I hope you have all the numbers you need. Again thanks for your help.

[William C.]

Re: carter carbs afb/wcfb

ok, the '459 intake is an AFB intake from the late '64 or '64 model year. the 829 intake is a wcfb intake from the 1958-61 era. the 3460 carb is for a powerglide equipped 1963 300 hp corvette, so it matches the intake. These afb setups used a stainless plate and insulating phenolic spacer under the carb the sequence is gasket between the manifold and carb, then the phenolic plate then the SS plate then the carb. If you have the '459 intake on the car, I'd stick with the AFB as that matches the manifold. Just be sure to use the proper baffle and insulator as described to keep the exhaust gasses from eating into the carb.

[Stuart F.]

Re: carter carbs afb/wcfb

Your AFB came off a 1963 w/automatic trans and was made in November 1962 (3460S) K2. Can't tell much about WCFB w/o a model/date.

Perhaps someone else has the manifold numbers handy.

Stu Fox

[Stephen R.]

Re: carter carbs afb/wcfb

Absolutely great! Thanks for the info. I'll pull the WCFB sometime this week and see if I can get the model number. The history of this car is that I bought it in 1974 as basically a running basket case. I was told that the engine in the car was "not running right" and it wasn't, so I trashed it and bought (in 1976) the current complete engine off of a guy who had parted out 85 to 90 vettes from 1955 to 1962. He basically specialized as a junk dealer in those old cars. I bought the engine because it was complete and supposedly ran however I tore it down and rebuilt it anyway. It was complete from fly wheel to fan, carb to oil pan. Paid $50 for it. The car itself had been through many owners in its short 15 years of life in 1974 and showed it. It looks a lot better now. But I am finding no matter what I do to the car, somebody has been there before me.

Finally what references are you using to cross the numbers with the years?

Many thanks again, I now know a little more history. Probably will go back to the AFB set up.
Steve

[Stuart F.]

Re: carter carbs afb/wcfb

Stephen;

On the AFB, it is pretty straight forward and is well documented in many publications, i.e. The 63 Corvette shop Manual, the NCRS TIM/JG, as well as Noland Adam's Restoration Guide. The 63 basically used only the AFB 3460S on L-75 engines with Powerglide Transmissions, and the 3461S for both the L-75 and L-76 engines with Manual Transmissions. Production started in late 1962, hense the carb date on yours of "K" (November) and "2" (1962).

The 3460S and 3461S carbs have shown up on some early 64 cars (L-75's only), as well as some late 63's have been known to have the 64 succeeding AFB series of carbs 3720S and 3721S, automatic and manual transmissions respectively. These carburetors continued on for several more years after (L-75's only) with several model revisions designated by suffix letters "A" and "B" (typ. 3720SA or 3721SB). The revisions were only due to some fine tuning of the jetting, i.e. primary and secondary main jets, primary metering rods, fixed low speed (idle) jets, and air bleeds.

The Unique carb in this whole bunch is the 3461S which was the only one used on the L-76 engine in 1963 only. If you had that one, you'd have yourself a rare prize. I know, because mine was stolen and replaced by a Corvette shop with a 3720SA. The same engine package in 1962 (340hp)had a different model carb due to a different ignition system, PCV and other off-engine considerations. The L-76 engine package in 1964 had many internal changes, and included the use of a Holley Carburetor.

The Carter AFB series never ceases to amaze me. Your story is the first one I've heard where a reported oddball AFB carb turned up and was from an actual Corvette application. There must be literally several hundred different AFB model carburetors out there for many GM, AMC, and Chrysler car models.

Stu Fox

[Stephen R.]

Re: carter carbs afb/wcfb

Thanks again for all of you help. Looks like I'm going back to the AFB since that manifold is now on the car.