xkeots

Hi All,

I took a ride last month and in 40 miles I used a full tank of fuel on my stock, all matching number 63 SWC.
The day after I had to have my right elbow reconstructed and I am doing pretty good. Not for heavy work, but I was able to track the leak to the Carb. all gaskets and the accelerator pump leaking on my Carter AFB 4bbl Carburetor. I was lucky the car didn't burn up.
I just finished rebuilding the carb but the manual choke is frozen.
Is there a way to free up inside the choke chamber the vacuum piston? I took the screw off in the choke chamber and the inside linkage is fine from the top butterfly to the choke chamber.
I was going to dip the chamber but I wanted to ask if that will free out any crud that in in the piston & chamber inside the choke body?
I sprayed Kroil & PB Blaster in it and it is moving very slightly. But not enough to make the choke work correctly.

Thanks Very Much,

Jack Miller
1963 SWC
1977 L-82

62Jeff

You may have to remove the choke piston.

Also, change your oil, it likely is saturated with gasoline. In fact I'd be surprised if you oil level is still "normal" after this, it is probably high.

xkeots

I didn't know that it comes out?
Are you positive? I don't want to break it.
Should I put the choke unit in a carb cleaner bath or soak it in Kroil or PB?

Thanks
Jack

62Jeff

Sorry, I'm tired and I might be confusing my carburetors.

Shouldn't hurt it to soak it in a cleaner.

http://www.corvettefever.com/techart...d/viewall.html

65GGvert

I recently had to remove the choke piston from the choke body because it was sticking. Mine is a 65 so I don't know if it's the same. It's a carter AFB. If you'll post a picture of the choke body, and it's the same, I can tell you how to get it out and sand it and put it back. It comes out without drilling or cutting anything, so post a picture before you do anything drastic. Here's a picture of the choke piston I have (bottom photo)

xkeots

It is the exact same. My choke piston is frozen in its (slot) cylinder. I let it soak in Kroil and now it is soaking in a gallon can of carb cleaner.
I was prying the rivet part with a screwdriver and the piston came up about 1/4 inch.
I stopped as I thought I was going to break the elbow, so I decided to soak it overnight with center screw out.
Please let me know what you did to get it out and clean it up.

Thanks,
Jack

xkeots

Thanks,
I was using that as a pre read.
Try this one, the picture story is killer! So is the quality.
http://helpwrench.com/forums/showthr...edlebrock-carb)

Jack

65GGvert

Please let me know what you did to get it out and clean it up.

Thanks,
Jack

I took out that flat head screw so the upper part could swing down a little, squirted some 3in1 oil into the top and let it soak down on the piston a little. Then used some needle nose pliers to pull the choke out the top, tilting the linkage to the right as it comes up so that it will clear the inside of the housing. When it got near the top, it was so tight that I thought it was going to break the linkage arm. After I finally got it out ( I had the choke ***'y off the carb by the way), I sanded the brass piston and rolled up some sandpaper and sanded inside the housing tube as best as I could with the paper wrapped around a foam medical mouth swab I had to put a little pressure on the sides. I ended up taking it in and out 4 or 5 times before I got it sanded down even enough to slide smoothly. The top of the housing tube must be a little smaller because it always really tightened up when the bottom of the piston reached that point. The weight of the piston, along with the small hole at the bottom providing vacuum to pull it down when the engine is running keep tension against the choke coil spring. Make sure you put the little o ring back in on the back of the housing that seals that small vacuum slot. It fits into a little indentation and is pulled tight when you tighten the three screws that hold the housing to the carb. I found a new one for sale, housing and piston assembled, for $60, so I put some extra pressure on getting it out knowing that if I broke it I could get a replacement. I found it on Ebay. At one point, I put a screwdriver at the bottom of the linkage near the piston and used it as a lever position to rotate the pliers on for more leverage. PM me if you want me to call you to clear up anything I said that may be confusing.

xkeots

I got it apart after a night in a carb bath and a day soaking in kroil. Then using a needle nose vise plier on the arm and tapped it out with a hammer, slowly. I had to bring the pieces to a carb rebuilder to hone and to re cap the vacuum hole as the piston and hole were out of round..

Thanks
Jack

30644

65GGvert -----

I am going through the same problem as the OP with '64 Carter AFB choke refurbish.

In post #8 you mention "The weight of the piston, along with the small hole at the bottom providing vacuum to pull it down when the engine is running keep tension against the choke coil spring. "

My choke piston was bound up but is now free and slides freely with a little manual push. I removed it and used 150 sandpaper to unbind it. Should the piston slide so freely that gravity pulls it down (toward the vacuum hole) before the engine is started? Mine slides, but does not slide that freely. I am afraid to sand the brass piston further as I do not want to make the fit nullify the effect of the vacuum in pulling the piston down. I think that the weight of the piston needs to cause movement so that the choke plate will close before the cold engine is started. Correct?

As my setup stands now, the choke plate never gets closed.

--Keith

65GGvert

Yes the weight of the piston should pull off the choke when you press the accelerator if the engine is warmed up fully. When the engine is cold, the choke spring should hold up the piston keeping the plate closed until it warms up. Adjust the choke so it stays fully closed cold and then opens fully when warm. With the choke spring off the car, the piston should fall freely with it's own weight and pull the choke plate open. Sanding it a little more won't hurt if it's still rubbing a little. Mine was only rubbing in the fully up or choke on position. Sanding took care of that. If you had the entire choke body off, make sure you put the tiny o ring between the body and the carb back on before you put the screws in to hold it in place. With the engine running, a small amount of vacuum is added to the bottom of the piston "tube" to assist in pulling the choke as far as the fast idle cam will allow it to drop. Once warm and accelerator is pressed and released, that will be completely off.
Edit: I just reread your question. The weight of the piston pulls the choke off. The choke spring pulls it on. But the piston has to be free in either case. You may just need to rotate your choke housing further clockwise to put more tension on the spring to pull the choke on. Make sure the hook in the spring is facing the correct direction to pull the choke on when rotating clockwise. The spring CAN be put in backwards so the hook is facing toward the back of the car when in place. The correct direction is with the hook facing toward the front of the car or your right as you look at it if it was mounted on the carb.

Frankie the Fink

Haven't had to do this yet but would be reluctant to sand it...I've always thought a little cleaning with a weapon bore brush and solvent might be the ticket but I've never tried it. Seems like carbon deposits are the culprit and they should scrub off with enough work.


The AFB is probably like the WCFB (not 100% sure though) and intake manifold pressure applied to the piston forces it to pull the choke off (not its weight).. If so, sanding the choke passage might affect this process.

65GGvert

Carbon deposits did not cause the problem on either the OP of this thread or on mine. The brass piston had "expanded" a little. In the OP's case, he had to go to a carb shop, had them remove the pressed in cap at the bottom of the body, hone out the bore, sand the piston and replace the cap. If the piston is binding, a little sanding will fix the problem. The weight of the piston will pull off the choke by itself if the choke spring is disconnected. With the spring connected, the vacuum will hold slight pressure against the spring so the choke moves open smoothly when warming up.

rdc

My '63 has a 250hp with a WCFB. The choke seems to work fine when cold (it idles fast on a cold start and will idle down with a tap of the accelerator). Once warm, the car idles very fast (around 1500rpm) almost every time I come to a stop. I can give the accelerator a quick pump and it will idle down to "normal" (about 700rpm). Could the "piston sticking" mentioned in this thread be the issue?

65GGvert

Probably not. Once the choke is off when you're driving, the piston is all the way to the bottom anyway. I guess if the choke were adjusted too rich, the spring might pull it up a little, but not likely if it idled down on the same run. I'd say one possibility might be sticking in the accelerator linkage or misadjusted fast idle cam. Next time, reach down and pull up the accelerator pedal and see if the idle drops. If it does, the return spring isn't pulling the linkage back to full position. May just need to lubricate the linkage points under the hood or under the dash.