AFB Carburetor Choke Piston

[Greg S.]

I have a 340 horse 327 with a correct 3269 AFB. After the engine runs at temperature for a while and then cools down the pull off piston in the choke sticks in the hot position. That means the choke will not set properly when trying to set it when the engine has cooled to room temp.

The carb is restored to as new condition. There is no carbon or coking in the piston's cylinder. The heat transfer tube in the exhaust manifold is stainless and new. I have heard this is a common problem. Does anyone have any solutions to avoid this problem?

[Christopher R.]

Re: AFB Carburetor Choke Piston

I had the same problem. I understand it is common with these carbs. I took mine part and cleaned it well with a solvent and a Q-tip. Then I lubricated the bore. Some lubricant that doesn't gunk up. Maybe graphite - I forget now. Works great now.

[Dick W.]

Re: AFB Carburetor Choke Piston

I have a 340 horse 327 with a correct 3269 AFB. After the engine runs at temperature for a while and then cools down the pull off piston in the choke sticks in the hot position. That means the choke will not set properly when trying to set it when the engine has cooled to room temp.

The carb is restored to as new condition. There is no carbon or coking in the piston's cylinder. The heat transfer tube in the exhaust manifold is stainless and new. I have heard this is a common problem. Does anyone have any solutions to avoid this problem?

It was a problem when they were new. I used to remove the piston, soak in carb cleaner, and lightly polish with crocus cloth

[Stuart F.]

Re: AFB Carburetor Choke Piston

I used to have that problem with my 63 340 hp (with either a 3461S and a 3720 SA). I went so far as to remove the end plug from the pull off cylinder to polish it out, and polished the piston as well. It would work good for awhile (one season) and then start acting up again, specially after a winter of inactivity. It seemed to be a film of white corrosion that would build up. After fighting this problem for probably 30 or 40 years I finally installed an electric choke conversion and capped off the fresh air tube. The piston still performs it's function, but does not corrode. My wires are clipped up high on the carb and the fresh air hose is still in place, so the casual observer at a cruisin seldom detects the mod.

Stu fox