1963 Carter AFB 3461S Choke Spring

[Frederick H.]

Looking to replace the choke spring as part of the carb rebuild - noticed the one from Zip does not have the same configuration where it engages the tang in the housing (doesn't appear as secure). I didn't see a matching part listed on Mike's Carburetor site either. Anyone have any luck for a source?

Thanks in Advance.
Fred

[Duke W.]

I wouldn't bet that you can find a NOS spring. Why do you think it needs to be replaced?

Duke

[Frederick H.]

I haven't investigated entirely yet but thought I would include a new spring with a fresh rebuild. I haven't referred to the photos in the shop manual yet nor taken the choke cover off the clean the piston (probably a good starting point). The car isn't driven much (was started yesterday) and it is plenty warm in the garage and outside here in Plano, TX., so not sure how much the choke will engage at this point.

Thanks.

[Duke W.]

Are you planning to remove the carburetor and do a complete overhaul? Do you have a 1963 Corvette Shop Manual and a "zip kit" with the parts required for a carb refresh. Do you know how many miles/years it's been since the carb was overhauled?

The recommended choke housing setting is one notch lean, but yours appears to be four notches rich. Why is that?

I order to get decent advice you need to clearly state symptoms and your intentions, and why you think the carb needs to be overhauled, if that's your intention. It is not clear to me.

Duke

[Frederick H.]

- I have a shop manual but will not be doing the overhaul. If my usual local shop or other source can get it done in time for the October judging, then I'll let them do it otherwise I just want to get the choke to pass for operations check, hence my initial post only about the spring. (Lots of other items to complete before judging).
- It's been close to ten years since last rebuild with little driving since.
- I do not know why the choke is set so far to the lean setting - I didn't set it.
I will check the shop manual for settings, clean the choke, and reset the lean/rich settings as first steps.

Thanks.

[Mark E.]

In the Quadrajet world, choke coil springs are application specific with a myriad of PNs available. If this is the case with AFBs, think twice before replacing the original coil with another which may be generic or incorrect.

[Thomas S.]

eBay, enter Carter AFB choke spring Many choices

[Frederick H.]

Thanks Mark and Thomas - yep, finding that there are many choices, most of which will probably not work. Will adjust the current spring back to a more reasonable setting and clean the piston before going any further.

Thanks.

[Duke W.]

The AFB is an excellent carburetor, but its Achilles Heel is the choke system. The choke "clean air" system tends to get dirty and the OE type oil -wetted air filter element is a primary culprit. Oil or heavy fuel vapors get drawn into the system coating the surfaces, which then attracts dirt. The result is that the choke vacuum break piston gets sticky, which degrades operation.

At room temperature when the throttle is opened the choke valve should fully close. If not then the choke system needs to be inspected and cleaned. It can be removed from the carburetor without removing the carburetor from the manifold. There is a tiny o-ring that seals the connection between the carburetor body and choke housing vacuum passage and this MUST be replaced when the choke housing is installed.

Other potential problem areas include the hot air tube in the exhaust manifold and the choke valve itself and linkage. Seal one end and blow through the other. There might be slight leakage, but if air flows freely the tube inside the exhaust manifold is likely rusted out.

Be sure the choke valve and link can be freely moved. Check the sides of the air horn for any sign that the sides of the valve are rubbing against the air horn. If so a little sanding might be required to allow the valve to move freely.

I believe the thermostatic choke spring can lose tension over time and use, which may not allow the cold valve to fully close even if the linkage and choke piston move freely. In this case the choke housing adjustment can be moved clockwise from the one notch lean recommended to the neutral or "rich side", and yours is already there. It is not on the lean side. Only adjust the choke housing position if the rest of the system moves freely. Don't use adjusting the choke housing as a "crutch" for a sticky vacuum break piston.

If you have an outside shop rebuild the carburetor I suggest you copy the applicable pages from your 1963 Corvette Shop Manual and give them to the shop. If they don't have this documentation there is no way they will be able to properly adjust the various settings and you will likely continue to have problems.

Duke

[Frederick H.]

Thanks Duke. I changed the air filter element to a standard AC element about a year ago after seeing a post (maybe yours?) about the issues with the original-style element.
The choke cover is set all the way over to lean, not rich based on the arrow on the cover (see photo).
I did see where the bottom of the choke valve is slightly scraping the side of the air horn as you mentioned and the choke valve closes to within an eighth-in or so if I give it a nudge (see photo).
As you mentioned, the choke spring may have weakened over time (this was my original thinking for changing it out).

Thanks again -will check items mentioned.

[Mark E.]

I'm not familiar with AFB, but if like Quadrajets, the choke plate can be aligned by loosening just a bit the retaining screws on the shaft and adjusting the plate. These screws are often staked to prevent them from falling out so avoid loosening any more than necessary and definitely do not try removing them... they'll probably snap.