63 340hp AFB carb woes

[Stuart F.]

1) I am currently on my second NOS correct model AFB carb, and am experiencing the same/similar problem for which I replaced the original carb. Several times each year I have to disassemble the choke assembly and clean up the "pull off piston". The car doesn't get driven more than about 1k/year, so there are periods of several weeks in between start ups (specially during the rainy season here in Florida). During these idle periods, it seems to build up a sort of white corrosion which binds up the choke so it won't close completely for startup, or open completely when fully warmed up. I usually have to take and massage the piston and little cylinder with emory cloth. The linkage and choke shaft work freely. I replaced the first carb because it got so bad that I believe that the choke housing itself was warped as I could not get it to work at all. That carb also had other issues as well, but maybe someday I will try again to resurrect it. With the current carb, most resently, I applied a little Lucas oil to the piston in an attempt to stop the corrosion (no other lubrication will stay for long as it gets sucked in and consumed). Well, it doesn't seem to corrode now, but is sluggish, i.e. you have to kick the throttle several times to get it fully closed or fully open. I am very careful when I disassemble and reassemble the choke too to make sure I don't let the hot air tube induce any tension on the choke cover (the tube must slide in freely before I tighten the nut, and the 3 cover screws are just tight enough to secure the cover to the housing). Has any one else with an AFB had similar choke issues and found any solutions?
2) A second item with my 340 hp w/AFB involves the throttle return spring. I understand it is again unique for this application; a white spring which attaches to a SS bracket bolted to the manifold. I have ordered new springs from several suppliers and they are all the same; the straight portion of the spring is too long. If used as is, it will not pull the throttle back to idle. I have had to cut them down and recurl the throttle end. If cut too short, the spring coils will engage the throttle linkage arm at WOT (not good). Accordingly, I have cut them down some, but they are still too weak to hold the throttle at idle. So, I have had to use a second 1/4" diameter spring in the spare hole in the bracket to a hole in the throttle arm. The white spring is in the only hole it will work in on the bracket, and is connected to the hole in the accelerator rod (just as is in the assembly manual). Anyone else had this problem and have a solution? Mine works fine now, but isn't correct.

[Clem Z.]

Re: 63 340hp AFB carb woes

1) I am currently on my second NOS correct model AFB carb, and am experiencing the same/similar problem for which I replaced the original carb. Several times each year I have to disassemble the choke assembly and clean up the "pull off piston". The car doesn't get driven more than about 1k/year, so there are periods of several weeks in between start ups (specially during the rainy season here in Florida). During these idle periods, it seems to build up a sort of white corrosion which binds up the choke so it won't close completely for startup, or open completely when fully warmed up. I usually have to take and massage the piston and little cylinder with emory cloth. The linkage and choke shaft work freely. I replaced the first carb because it got so bad that I believe that the choke housing itself was warped as I could not get it to work at all. That carb also had other issues as well, but maybe someday I will try again to resurrect it. With the current carb, most resently, I applied a little Lucas oil to the piston in an attempt to stop the corrosion (no other lubrication will stay for long as it gets sucked in and consumed). Well, it doesn't seem to corrode now, but is sluggish, i.e. you have to kick the throttle several times to get it fully closed or fully open. I am very careful when I disassemble and reassemble the choke too to make sure I don't let the hot air tube induce any tension on the choke cover (the tube must slide in freely before I tighten the nut, and the 3 cover screws are just tight enough to secure the cover to the housing). Has any one else with an AFB had similar choke issues and found any solutions?
2) A second item with my 340 hp w/AFB involves the throttle return spring. I understand it is again unique for this application; a white spring which attaches to a SS bracket bolted to the manifold. I have ordered new springs from several suppliers and they are all the same; the straight portion of the spring is too long. If used as is, it will not pull the throttle back to idle. I have had to cut them down and recurl the throttle end. If cut too short, the spring coils will engage the throttle linkage arm at WOT (not good). Accordingly, I have cut them down some, but they are still too weak to hold the throttle at idle. So, I have had to use a second 1/4" diameter spring in the spare hole in the bracket to a hole in the throttle arm. The white spring is in the only hole it will work in on the bracket, and is connected to the hole in the accelerator rod (just as is in the assembly manual). Anyone else had this problem and have a solution? Mine works fine now, but isn't correct.

sounds like the choke heat tube in the exhaust manifold is letting exhaust gas into the choke housing because it is rusted thru. do you have the setup that pulls clean air from the carb throat thru the choke system ???

[Stuart F.]

Re: 63 340hp AFB carb woes

Thanks for that observation. As wordy as I got, I forgot to mention I checked for that and have watched for it for some time, but do not see any sign of it. I have dealt with just that same condition on other Chevys from Back in the Day. Usually you see evidence of black cruddy exhaust residue plugging up the choke. Mine is as clean as can be, and I think the Vette system of taking clean air from the carb air horn in a closed loop fashion has eleminated the chance for splash up water or condensation from entering that X-tube.

[Mike M.]

Re: 63 340hp AFB carb woes

White I think is the wrong color. Most suppliers sell this spring as the correct spring but it is to long. The black or one used on 63 thru 67 in DR. rebuild #3459204 is correct others have the same spring. The judging guide calls for the black phosphate spring.

[Ray G.]

Re: 63 340hp AFB carb woes

Hello;

One idea popped into my pea brain while reading your post.

Try making a temporary heat stove by wrapping a piece on tubing around the exhaust manifold thereby bypassing the factory set up.

Hope that helps.
Ray

[Michael H.]

Re: 63 340hp AFB carb woes

White I think is the wrong color. Most suppliers sell this spring as the correct spring but it is to long. The black or one used on 63 thru 67 in DR. rebuild #3459204 is correct others have the same spring. The judging guide calls for the black phosphate spring.

Mike is correct. The long white spring was used for 62 340 Hp but not 63. The correct spring for 63 was shorter and either painted or plated black. Believe the correct part number is 3830222?