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Idle Mixtures screws do nothing - Can't tune my car!

Old 07-04-2011, 12:23 PM
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The seats could maybe be reamed, but finding the reamer would be a feat of miraculous proportion.

I've used and worked on dozens of these from OE, Carter, Edelbrock, all of them. I've never seen a blunt screw like that. I've seen a conical taper and a step taper. The step taper to allow more flow. It is not uncommon for these carbs to be all kinds of jacked up my people that lack the right "technique" to work on them without damage.

IF there is a solution, this guy will have it:
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Old 07-04-2011, 02:34 PM
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I doubt the screws were like that stock, I've looked up pictures online and all of them come to some sort of point. I went ahead and ordered them from amazon, $9.11 with free 2-day shipping, better overall price than summit and local auto stores. Here's the link to what I bought and a picture of what it should look like:

The tips themselves were kind of different from each other, one was pushed in (concave) and the other was more rounded, but they were both pretty much the same length. I'm sure over the past 4 years they have not been treated well by myself and/or my dad, they seem very delicate, so hopefully replacement screws will solve the problem. If not, I'll look into ports being clogged. If the carburetor ends up being shot because of this I think my dad has a extra holley carb that he can't use on his Cobra Jet, it should be the right cfm for my car.

Thanks for all the help, any other potential causes that could be working in conjunction with the bad needle screws? How do I know if it is simply dumping too much fuel in? The car used to run just fine so I'm not sure if this would be the issue, but I wouldn't know for sure.
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Old 07-04-2011, 02:53 PM
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you could always look for vac leaks...I guess
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Old 07-05-2011, 01:42 AM
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If the idle mixture screws you showed that look like the tips are broken off really do have the tips broken off then those tips have to be somewhere. My first guess is that they were over tightened into the carb and now the tips are stuck in their seats. If this is true then installing new mixture screw on top on the broken tips is just going to ruin the new screws. I would suggest doing everything you can to see if the tips are still in the carb before installing the new screws. On most carbs if the screw is all the way in you can see it in the throat of the carb when you open the throttle wide open. I would suggest doing that at a minimum prior to installing the new screws. It might actually be a good idea to take the carb off and at least do a partial disassembly and see if you can locate the tips.
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