I have a 1975 E150 with a 300 and a non electronic Carter carb. Normally, it runs like a top. When I push the pedal to the floor, the choke actuates. I blip the throttle after startup, and it deactivates. When warm, the choke won't engage.
This morning, I had no problems starting when it was 5 degrees out. I drove for 20 minutes and turned it off. Fifteen minutes later, I tried to start it and it was warm enough to not actuate the choke, but too cold to start without it.
Is there a way that I can adjust the choke to activate at a warmer temperature?
I notice that there is a tube that runs through the exhaust manifold. Would I be correct in assuming that it is using that as a temperature reference?
I am hoping to eventually switch to the FI manifolds and I was wondering what effect omitting or bypassing that tube would have on my choke.

 

The tube draws hot air up from the exhaust manifold. Without it the choke will stay 'on' for much longer than necessary. Replace it. A piece of 1/4 brake line makes a suitable substitute. A heat sock over it is even better.

 

So, if I reroute the tube to not come in contact with the exhaust, I could set the choke on startup even if the engine is warm?
Ideally, I would like to be able to set the choke on startup as desired, but it won't actuate at all during the summer months when I could occasionally use the choke on a cool, sub 60 degree morning startup. .

 

The end of the tube must be inserted into a 1/4" hole in the exhaust manifold.

 

While the stock setup works great, I would like to swap the log manifold to the dual efi manifolds setup. I read that you will want to bend the tubing to wrap around one of the manifolds and cut a tin can to fit over it.
I've also read about making a heating plate to route coolant through the intake manifold cavity.

I recently swapped in a K&N filter and noticed that my idle seems to wander. Like it's about ready to stall and then catches itself. I adjusted the idle mixture, climactic choke mixture ****, and idle speed, and now doesn't seem so bad, but the wandering idle still persists. I'm going to swap the stock filter back on and make sure that is the problem.
What kind of tuning do these carbs need when flow rates are increased?

 

I thought I was going mad making adjustments to this carb, but I finally figured out my wandering idle problem. I've got a leaking distributor advance diaphragm. Will I be able to change that out without removing or disassembling my distributor?

 

You were right about the choke tubing being bad. Mine broke off in the manifold. Is there a way to reroute the tubing through it?

 

Drill it out (the broke-off piece) and use a piece of SS brake line like FTF suggested. That hole doesn't go through the manifold...it's a dead end.

 

You see in your picture the pipe is broke at the top AND at 90 degree plug on the bottom. One of the pipes goes to your choke chamber. The other SHOULD, go to a fitting on the carb near the air horn (choke plate area). This line allows filtered air to pass thru the manifold and to and thru the pipe to the choke chamber. Now depending on if your carb has an internal or external choke pull off. If internal there is a little piston that pulls the choke plate open a certain degree on start up cold. That piston is operated by engine vacuum. That vacuum also draws the hot air from the manifold tube in to the choke chamber to warm the bi-metalic spring and allow the choke to open. That vacuum by the piston is a calculated leak. So now you have been running with a broken tube and sucking rust, scale, air-born dirt into the choke chamber, possibly gumming up the piston and plugging the vacuum source, which may be affecting your idle. You should not have to re choke a warm engine. Look for another reason as hot restart problem.