63 choke issue

[Bruce D.]

The choke on my 63 is stuck. after taking it apart the little arm/sleeve in the body of the choke temp unit is stuck and will not move it and out. this keeps the choke butterfly from closing. what does this sleeve/piston do for the choke and how can I get if to free up and move in and out? I tried some liguid wrench but am trying to be careful not to break something since I am not sure how it works. thanks

[Bill W.]

Re: 63 choke issue

Bruce,
We need more info....carb or FI. AFB or WCFB?

[Harry S.]

Re: 63 choke issue

The choke on my 63 is stuck. after taking it apart the little arm/sleeve in the body of the choke temp unit is stuck and will not move it and out. this keeps the choke butterfly from closing. what does this sleeve/piston do for the choke and how can I get if to free up and move in and out? I tried some liguid wrench but am trying to be careful not to break something since I am not sure how it works. thanks

This is a problem with 63 carb's and chokes. The piston gets hung up because of a carbon buildup. Use a solution to breakup the carbon and get it out. Clean everything and sand with 3600 grit wet sandpaper to get a smooth surface. Also sand the piston tube if you can.

This should help.

Bruce, I just remembered, there is a rubber o-ring between the choke and the carb. to secure a vacuum to the piston. Make sure that hole is open also and the o-ring is in place.

[Bruce D.]

Re: 63 choke issue

Reply 340 hp AFB Harry: any suggestions about what solution is best to free up the carbon. I thought that piston came out previously but was not aware of the vacuum that is used to move the piston. I will check for the O ring.

[Timothy B.]

Re: 63 choke issue

Bruce,

The choke piston is stuck because of lack of maintenance or a small exhaust leak in the hot air tube that runs through the exhaust manifold. The adjustment of this part is very important to proper choke operation, soak it with Kroil and keep working it without bending the rod.

When adjusted, vacuum from the engine pulls this piston to open the choke blade and the tang on the piston rod balances against the choke spring. As the choke spring get heated by engine vacuum pulling hot air through the exhaust manifold and choke housing, the spring will relax to allow the piston to move the choke to a open position.

These two parts (spring and piston) balance against each other so there adjustment is important. The 1963 shop manual has a good detailed section on AFB adjustments including the choke vacuum break (piston).

[Stuart F.]

Re: 63 choke issue

I used to fight this condition almost on a yearly basis, (with either a standard 3461S or a replacement 3721SB) but I found the culprit to be a white like corrosion. It is hard to clean the cylinder unless you pull the end plug which I would not recommend. So, your best bet is to clean the piston and be prepared to do it again in another year or two. That's the nature of the beast as long as you use the stock hot air source arrangement. The choke housing is made of some type of pot metal while the carb body is aluminum. I suspected there was some sort of galvanic action going on that produced the white corrosion. If your tube is actually pulling in exhaust carbon, then your stove tube is rusted through and will have to be replaced. However, having gone through this several times back in the day, I can assure you that if this is the problem you can not miss it. The entire choke housing would be full of black carbon soot - not just the vacuum pull off.

My solution, which the pureists don't like, is to go to a good electric choke and eliminate the hot air tube from the circuit. I did that years ago and have had no trouble since. I still get very good engine vacuum pull off action which now is assisted by the choke spring which captures the tang to both push and pull the pull off linkage. BTW, I can chage my choke back to stock in a matter of mere minutes for car shows.

Stu Fox

[Dan B.]

Re: 63 choke issue

Bruce, with the choke housing off the car and the cover and gaskets removed, spray it up inside the piston area and through the back side vacuum hole with some Gumout (where it mounts) then remove the piston arm screw and manually try to work it free and out. If it's really stubborn, let it soak overnight in a can of solvent and repeat. Another trick I use is to apply compressed air (with the piston in place) through the rear suction hole. It will blow the end plug out without and damage and allow you the best access to the piston and cleaning the cylinder. It is easily reinstalled. Dan

[Bruce D.]

Re: 63 choke issue

The above suggestions worked fine and I got the piston out and cleaned the housing and the piston with some fine emery paper after soaking the entire unit. All works fine now. thanks for the responses.