Thermostatic choke system?

Yesterday, I pulled my intake and exhaust manifold and attempted to rebuild my thermostatic choke system. As you can tell, my truck has an aftermarket carb on it. I hooked up the fresh "cool" air side and then moved on the the "hot" side that screws into the choke. Upon looking in the threaded hookup on the carb, it is closed off (goes nowhere).

Does this mean my choke does not use the thermostatic system?

It starts fine all day, every day. My only issue is when it is cold, it stalls when I come to a stop. Once the truck is warmed up, the stalling stops and it runs like normal.

Is is as simple as adjusting the carb to idle at a higher RPM in the winter?

In the very least, I was able to put a new manifold gasket on so the entire venture wasn't a total loss!

Just having the tube hooked up would help with heat.   I've experienced carb icing at 68F with a broken thermostatic tube before.  By the time you pop the hood to find out what is going on it defrosts.  Could be a possibility of what is happening to you as well.

Some different possibilities for consideration . . .

On my carb there is a hole that goes from beneath the choke cap, to the threaded hole in the picture.  You have to remove the choke cap to see it.  With the carb being aftermarket, you might have to drill the hole?  I've never seen one that didn't have it, and to just have a blind fitting seems weird.  In the aftermarket world though, anything is a possibility.

Another thing, modern gasoline does not have the fuel antifreeze additive, for carbureted vehicles, it once had in the past.  Using a fuel system antifreeze might be prudent, especially in colder climates.

I also notice this carb has a block off plate for the feedback solenoid.  So this Carb is not a true non-feedback carb.  If this Carb is a one size fits all Carb, I'd try to find a better fit for your engine and engine calibration.

And Finally, your engine calibration may need the installation of a anti-stall dashpot, on the throttle linkage.  Dashpots came in mechanical and electronic versions.  The mechanical version is a device with spring action that reduces the throttle closed gradually to  prevent stalls. Without it the throttle shuts abruptly causing stalls.  Especially at Stops.  The electronic version was controlled by a computer or switched or solenoid control.

Hopefully one of these suggestions will help.

You can try and richen the choke cap a little as it sounds like the choke may be pulling off to soon.

You also need to check the heat riser valve, it blows hot exh on the floor of the intake to help in cold weather running.

The other is the hot air intake of the air filter assy.
There should be a paper hose from the snorkel to a tin around the exh manifold.
There is a valve in the snorkel that closes off cold air from the grille and pulls in hot air.
As the motor heats up the valve moves to let more cool air in.

Between the heat riser, the air filter hot air and the choke adjusted right is all needed to make the motor run right at all times.
Dave ----

I'm having similar issues with the yfa on Brutus.  The choke is pulling off to soon.  Whenever you come to a stop, the truck acts like it wants to kill but it never does, it stumbles, then it will catch itself.  I never could figure out what this problem is.

Sounds like the choke is set too lean, and needs to be richened up slightly.

If the choke doesn't fully open after adjustment, when fully warm, then there is a problem with one of the systems  that Fuzzface or I mentioned earlier in the thread.

Or the choke cap spring is weak and needs replaced.

I'll take all these thoughts into account and keep tinkering with it. Thanks for all the help!

The chokes often require seasonal adjustments. See if this link helps:

https://www.ford-trucks.com/forums/1110073-choke-adjustment-101-a.html

They shouldn't require seasonal adjustments if everything works perfect, but often times they do. Imperfect world, and parts age etc. . .

Some California YFA's are not adjustable at all from new as example. They are factory set and forget it. These can be a pain, especially if they are off or worn slightly.  Believe me.

I set mine about 6 years ago and I haven't had to make any seasonal adjustments.  It starts and runs great all year round.  I don't have to make any seasonal mixture adjustments either.  In fact, I haven't had to adjust *anything* on my carburetor since 2016.

I am running the stock thermostatic "hot air" choke with electric assist.  The thermostatic air cleaner probably helps with that as well.  


I set the idle mixture with the air cleaner installed and the engine fully warmed up.  And I also set the choke fast idle speed with the engine fully warmed up. (That is actually how you are supposed to adjust it.)

It is truly amazing how well a carbureted vehicle can run when all of the parts are there and everything is adjusted correctly.