Question on Carter AFB carb for 63

[Mel H.]

Is there a difference in AFB carbs used on the 300hp and 340 hp cars in 1963? Book lists both as having same carb number 3461s, and same carb part number. So, are they interchangeable and will either suffice for NCRS?

Thnx in advance for any calrification anyone can bring.

[Duke W.]

Re: Question on Carter AFB carb for 63

Yes, 340 HP and 300 HP with man. trans used the exact same carburetor, and they are interchangeable. You only need one with a ballpark date code for either engine from either engine; 300 HP with PG used the 3460S

Duke

[Richard M.]

Re: Question on Carter AFB carb for 63

Here are a few shots of the 3460S on our old '63. Only difference I believe is the kickdown lever hole and maybe, the port fitting for the modulator vacuum line......Rich

[Mel H.]

Re: Question on Carter AFB carb for 63

Thanks guys. I thought the 300hp carb might be same as my 340hp (has wrong date code). I couldn't find any differences unless its something internal (jetting, etc).

Local guy selling his 300 hp 3461s. Will see him this weekend.

[Stuart F.]

Re: Question on Carter AFB carb for 63

Richard;

Where do you have your return spring hooked to on the carb? It's hard to tell by the picture, but it looks like you are using a cotter pin on the rod. Many AFB's do not have the hole in the throttle arm for the spring (have never done a study, but different sources show the spring hooked in place of the cotter pin). I have both a 3720SA and a 3721SB (replacement carb) and each is different. Also, I have always had to add a small booster spring and have done that differently for each model.

Stu Fox

[Richard M.]

Re: Question on Carter AFB carb for 63

I had to find some photos.....car was sold last year.

As I recall, the correct(repro) spring was not strong enough. I used the one that was there with the Carter Competition AFB that was on the car when I got it.... Beefier. The AIM shows a spring hole for the 250 hp WCFB, but the L75,76 page has no detail. As you can see I hooked it on just below the link on the arm itself. I like cotter pins to hold the rod, not thin spring material. Never had a problem.

I found this correct AFB at Kissimmee in '08. Actually my wife pointed it out to me at the swap meet area. She said, "What about that one?", pointing down to a bunch of carbs on a blue tarp. I said "I doubt it", with sarcasmWell I went over and there it was, correct date and all.

Rich

[Stuart F.]

Re: Question on Carter AFB carb for 63

Richard;

For years I struggled trying to get a "white" return spring (as specified) to work on my 63. The only way I could was to cut down the long end and bend a new hook on it. I ordered from about 3 or 4 sources, and they were all alike. They all listed the white spring for 63's. Finally, I went to the later 64 and up black spring which fit perfectly, but (as you say) is a little weak (irratic idle speed control). I found that by adding a light 1/4" dia spring was just enough to give me the feel and control I desired. It doesn't look pretty, but does the job and does not interfere with the linkage.

As for the cotter pin used to secure the throttle rod, well, I think the spring is as good at least for security. It is a hard material and not likely to shear any sooner than the pin. The pin, however, may give you a better fit (less slop).

We'll look for you at the winter meet.

Stu Fox

[Jack H.]

Re: Question on Carter AFB carb for 63

Consider taking the spring of your choice (based on performance), stretching it out just a tad, then hitting it with 'rattle can' paint of the color needed to make the judges happy!

[Duke W.]

Re: Question on Carter AFB carb for 63

My 340 HP used the spring end to secure the throttle rod to the carb rod bracket.

The AIM shows the WCFB as having a cotter pin to secure the throttle pull rod to the carb throttle lever with the throttle return spring attached to a small hole in the throttle lever below the throttle pull rod hole (Sect. 6 Sheet C1.00). Also note the "existing bracket", which implies that this was installed at the Flint engine plant.

My 3461S has no such specific hole for the throttle return spring, so the only way to attach it is to the cotter pin hole in the pull rod, however, the L-75/76 option section does not specifically show this deviation from "regular production".

Since the L-75/76 section does not call out specific spring or ground bracket, they are the same as "regular production" i.e. the WCFB

Look at Sect. 0 Sheet 1.00, Introduction, fifth paragraph:

OPTIONS WITH ITEMS VARYING IN ASSEMBLY FROM REGULAR PRODUCTION ARE ILLUSTRATED. ITEMS LISTED WITHIN ILLUSTRATED OPTIONS AND INSTALLED THE SAME AS REGULAR PRODUCTION ARE INDICATED BY SYMBOL. (SEE SYMBOL SHEET-SHEET 3.00)

Duke

[Stuart F.]

Re: Question on Carter AFB carb for 63

Being as how I got forced to go with a replacement 3721SB when my 3461S was lifted, I have the good fortune of having the hole in the throttle lever. But, I use it for my small booster spring and retain the main return spring through throttle rod. This works best for me. When, in the course of experimenting with the 3720SA that I have, that carb does not have the hole in the throttle lever. I then use a linkage ball swival fitting in the PG kick down attachment hole to apply my booster spring from it to a small bracket off my top rear valve cover screw (all stuff you didn't need to know).

On a side note, neither the AIM or the Judging Guide call for a white return spring, rather they say "black" as with the 64.

Stu Fox

[Richard M.]

Re: Question on Carter AFB carb for 63

...since we deviated from the OP topic(aka "hi-jacked"), sorry Mel. It appears we helped answer your questions and then continued to talk about other related stuff. This is good info so it's good to continue.....


On my '59 dual four setup I forgot what I did so I had to check.

I decided way back when, obviously, to use the cotter pin in the secondary WCFB lever to throttle rod and set the spring as shown on the link rod between the flanges of the lever and rod end bracket. This was in opposition to the AIM method of hooking the spring end into the big hole in the link end. Not "typical" but IMO "better". Of course in '08 when I got it judged I had it in the "correct" placement. When I got home I put it back to "my" method.

I just added some grease and since the secondaries rarely kick-in, everything is fine with no noticeable wear. I did this mod in '95 when I rebuilt the engine.

Rich

[Stuart F.]

Re: Question on Carter AFB carb for 63

Yes, I guess we did change the subject to: " Springs and things". Sorry, but it is still interesting stuff. All my set ups, changes or modifications were intended for full and best function. When I had dual quads, and the price of gas was .35 cents/gallon, I had those suckers open at every opportunity, like going under a viaduct just to hear the stages kick in and echo. That was cool!

Stu Fox

[Richard M.]

Re: Question on Carter AFB carb for 63

.....and the price of gas was .35 cents/gallon, I had those suckers open at every opportunity, like going under a viaduct just to hear the stages kick in and echo. That was cool!

Stu Fox

Yes very cool......my favorite sound when I get on mine too.

[Mel H.]

Re: Question on Carter AFB carb for 63

Not really hijacking guys.. more a continuation on related issues. I just appreciate confirming the carbs on 300s and 340s (MT) are virtually identical.

And to your point on the spring connection/color, I noted in Noland Adams restoration book a couple engine pictures showing the spring hook-up appears to be thru the hole in the accelerator linkage rod.. (had to use a magifying glass to see it... I know, pretty lame, right?) And I recognize these may not be of original condition cars, but being in his book brings some measure of credibility. And it also shows the spring is black.