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Old 08-21-2012, 08:44 AM   #1
Pickles_99

 
Join Date: Jun 2012
Vehicle: 1966 Ford Mustang Coupe
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Default Carb float and mixture screw questions.

Just cleaned and rebuilt carb (Autolite 2100 2v) and followed manual's recommendations for specs/measurements. Seems to be running well so far. Looking for feedback on what the symptoms of an improperly set float and mixture screws would be. I've turned the screws anywhere from 1 1/4 to 2 1/2 turns out while no real noticeable changes in rpms. Is that normal?

Also. . .I don't have the choke tube connected to the autochoke housing yet. Tube is broken off in the manifold. Does this mean the autochoke isn't working?
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Old 08-22-2012, 04:17 PM   #2
jlg2002
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I like your questions short and concise!

The way i was taught to adjust the idle screws and practiced in my days of being a professional tune up man is:

1. Set the idle speed to around 700-800 rpm
2. Using a tach or vacuum gauge adjust each needle until the gauge drops just a little then reverse a little bit 1/8 turn max.
Also, the choke tube has a small vacuum leak by design to pull the heated air up from the manifold. If you're not going to put a tube in you need to block the choke housing port.

The auto choke is working if when you depress the throttle to the floor (1 time) when cold the choke butterfly should go closed. What isn't going to happen is a quick warmup as the tube provides the heat to warm the bimetallic spring in the choke cap. this will result in the fast idle staying too high for a long time.

I suggest you replace the tube as soon as you can.
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Old 08-23-2012, 08:12 AM   #3
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Thanks, very helpful. I hopefully will be drilling out the broken tube from the manifold this weekend and hooking up properly.

How about the float? What are symptoms of an improperly set float? The only issue I have right now is a slight hesitation when first accelerating.
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Old 08-23-2012, 12:42 PM   #4
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And while I am at it, I have choke plate questions. When the car is cold, should the plate be completely closed? Should it open when the throttle is depressed? Once in a while I'll have a hard time starting the car. Each time this happens, I notice the choke plate is fully closed. I then open it slightly (with my finger) and the car starts.
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Old 08-23-2012, 05:33 PM   #5
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Quote:
Originally Posted by Pickles_99 View Post
And while I am at it, I have choke plate questions. When the car is cold, should the plate be completely closed? Should it open when the throttle is depressed? Once in a while I'll have a hard time starting the car. Each time this happens, I notice the choke plate is fully closed. I then open it slightly (with my finger) and the car starts.
By design, the choke plate tension is set by the index position of the black cap that covers the choke housing, unless you live where it's really,y really cold, that index is usually best set at the middle mark. Once set, there is a small vacuum operated diaphragm (called the choke pull off) on the right side of the carb that is supposed to pull the choke plate open to a specified position when you start the engine. you set that opening by inserting a specific drill bit between the carb throat and the plate edge and then bending the small linkage that attaches the diaphragm to the the choke plate. If you don't have the carb with the pull off, there is screw near the top of the choke housing that you adjust until the plate has a 1/16 in gap. this should be done before the choke spring is installed. You may need to Google for a photo of your carb to see what i'm discussing if it isn't apparent to you.

If this component is malfunctioning it will result in what you've described.
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Old 08-24-2012, 10:00 AM   #6
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I have the screw set-up and I did set it as you mentioned. Going to reset it again this weekend after connecting choke tube to the carb. Thanks for your input.
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Old 08-24-2012, 10:00 AM
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