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Forgive the relative inexperience of my question, but my 68 289 coupe is my very first car:

I have had problems with my car dying both before the car has heated up and been driven a few blocks and also if I rev the engine too much and don't slowly let off the gas. Any suggestions about the reasons for this would help, but I believe that it has to do with my carburetor choke and fast idle. I wanted to adjust both of them, but haven't been able to find out how.

The carburetor is NOT stock, since the guy before me put in a Holley 750 double pumper. The only books I have are ones that deal only with mustang restoration, and don't have any information regarding my carburetor. I can't seem to figure out how to do these adjustments, so any info would help.
 

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If you look on the sides of the front plate of the carb, you sill see two little screws. These will be your idle adjustment screws. They adjust the fuel/air ratio AT IDLE. Adjust them first to get as smooth an idle as possible. The fast idle is nother screw on the linkage, but don't change it just to keep it running. If the idle speed is fast enough already, try to fix the problem instead of applying a band aid! The fast idle screw is in the linkage beneath the choke. Do not adjust this unless it idles too slow when cold outside. If the fast idle isn't actuating, it's because the choke isn't closing.

You forgot to mention if you have an electric choke. On the dbl pumper I will assume this is what you have. Let the car set overnight to make sure it is cooled. Remove the air cleaner (engine off) and look to see if the choke is closed, or nearly so at this time of year. You may need to manually actuate the accelerator linkage to allow the choke to snap shut. If it does, you're good to go. If not, loosen the cap on the choke and set it so it will close. Remember you will have to manually move the linkage to allow the choke to close.

Start the car without stepping on the accelerator pedal. It should start at a fast idle if the choke is actuating the fast idle mechanism. It will come off fast idle if you step on the gas pedal and then release it.

Clear as mud? Really pretty easy, I just make it sound hard. Give it a go, and get back to us.
 

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just something to add, isn't that 750 a bit big for the 289? I have a 351w with a 600 cfm holly dbl pumper on mine. Just to make sure, i guess you could check the back of the choke tower for the list number and look it up on the internet or in a book to see what you have. I dunno how your engines built, but since reading this forum, a mild engine won't run good with such a big carb. I even tried a edelbrock 750 on mine to test it out and the 600 runs far better. good luck
 

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Yep, I agree... it should be closer to 500 than 750.
 

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I have recently argued against carb formula and have often written that naaa, you can use your big carb fine. But in your case, you might have too much carb or at least wrong type of carb. Double pumpers have mechanical secondaries, it opens both sides independent of what engine thinks it needs. I don't think you would have this kind of a problem with 750 cfm vacuum secondary carb.

What tranny you have?
Is the engine stock, mild, middle or much modified?

If you have an automatic and more mild than wild engine, I would suggest swapping in 600Vacuum secondary unit.
 
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