AFB Choke Spring
The attached photos show two AFB choke springs. The one with the fewest coils appears to be correct for my 3269 from a 62 340 SHP. The other can be used but it will index the indicator on the choke housing in the wrong place. I need a correct spring for a second 3269 that I have. I don't know much about these springs. I have several other springs, all indexed differently. Is there a source for ordering a new spring indexed for a specific application? I know I can order these with the heat sink from Corvette Central and others vendors but they seem to be indexed incorrectly.
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Re: AFB Choke Spring
Grey,
The spring on the right almost looks like it's been cut and bent. -
Re: AFB Choke Spring
Greg;
I have the same issue on my 1963 AFB, and have tried a few springs, including reproductions from places like Paragon.. What I find is that if I index as per the manual, the choke will not close and the high idle cam will not get set... I just start the car cold a few mornings making an adjustment each time until I get it to operate correctly on a consistent basis... Today my index mark is basically way off to the left (rich) side but she works like a champ...
JoelComment
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Re: AFB Choke Spring
Basically, what I've learned is that if it does not index right, then it is not for your application. My stock spring and housing worked fine for many many years. I removed it and packed it away because of the internals (pull off piston & linkage) would not work well for long if I used it with air from the hot air tube system (air cleaner thru manifold back to choke housing). I am using an aftermarket electric choke which, ironically, indexes perfectly. It has made my life much happier as I no longer have to mess with cleaning the choke once a year as before. If I ever was to go back to the stock appearing unit, I would still use the aftermarket spring. The reason is that it captures the pull off link rather than merely push on it to close the choke, i.e. it pushes it and pulls it in response to its cooling and heating both. The pull off piston linkage is still in play in order to connect properly to the fast idle linkage, but it is now more just along for the ride (so to speak). Without the hot air it no longer gets the white corrosion build up which used to bind it up in the past. The warm up cycle is very smooth.
Stu foxComment
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Re: AFB Choke Spring
Hi Stu;
Ahh very interesting! I never realized that there are different springs for different applications....
I've been running the original hot air tube system for about 4 years now without a problem...
All things being equal, I would suspect that using a different spring would not be a problem once you get it indexed properly.. In any event, this will give me one more thing to look for this year at Carlisle!!
Regards,
JoelComment
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Re: AFB Choke Spring
Joel;
Over the course of time, I have seen numerous AFB choke housing designs on the many many AFB models out there for different applications. I had one that was used on an American Motors application that had the hot air tube connected to the metal housing and often thought I'd like to try that with an electric choke so I could have both features fully functional. That was when I thought maybe the hot air bleed meant something to the idle mixture or low speed circuit operation of the carb. Then I tested the vacuum pull at the choke and only found about 1" or less Hg there (choke open or closed) and determined it was not relevent. I have tried different brass pistons and linkages from different models as well as different choke housings and always had the same problem with that white corrosion build up in the housing cylinder. I would clean the piston and housing with emory cloth and it would last about a year maybe two before the choke would start hanging up again.
I wanted to play more with that AM AFB that I had as it was brand new, picked it up at a garage sale, but guess I gave it away along with my Holley stuff to a kid down the street before our last move here to Florida. It had real small venturis and I thought it would make a great economy carb.
Stu FoxComment
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Re: AFB Choke Spring
I have also fought with keeping the small piston from sticking due to contaminants drawn into the housing. Some housings have a flat plate between the spring and the housing. My carbs do not have this flat plate. Do you think it would help to have the flat plate installed?
I looked in the Corvette Central on-line catalog. It shows the choke spring with and without the heat sink. Both springs are indexed differently as shown in the attached pictures. The spring without the heat sink seems to be correctly oriented. The first picture shows the springs I have installed in a choke cover. The one on the right will line up the index mark on the cover correctly. It is lined up like the CC spring without the heat sink. I will take a chance and order the spring from Corvette Central but I wonder if the picture is an accurate representation.Comment
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Re: AFB Choke Spring
Greg;
Most of the choke assemblies I have seen for some time now use a thin plate or disc inside. I believe it is there to form a "chamber" to contain the heated air around the spring and shield the "pull off" mechanism from direct exposure to it (probably to limit the contamination of the mechanism). I would find one that will fit if you can. They do have both a hole for the internal mounting screw as well as an open slot (arc) which corresponds to the travel of the mechanism arm.
Stu FoxComment
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Re: AFB Choke Spring
There is a circulation path that the hot air follows and the plate need to be there.
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