260z to 240z flat top to round top su conversion

[Captain Obvious]

When you say you have a leak in your throttle butterfly, I'm assuming you mean you have a leak around your throttle shaft where it meets the carb body? Your throttle butterfly is supposed to leak. That's how the engine gets it's air and fuel. But assuming you meant a leaky throttle shaft... I doubt you have enough of a leak to require 5-7 turns down on the mixture nut. If that truly is the case, then your carbs are all wallowed out and need to be repaired or replaced.

I can't figure out what you are talking about when you say "the linkage bar/balance screw that shuts the car off smoothly". I have no idea what that means.

Might I humbly suggest that you look through the factory service manual and use the same terms for parts that are in the manual. That standardization of terms would make troubleshooting a lot easier. :bulb:

[Guest tmsaws]

I'm figuring it out as I go along.....one problem after another. yes, throttle shaft is correct though. I sprayed a little carb cleaner around the throttle shaft while the car was idling and the idle speed dropped. it's just weird because these are brand new carbs, I don't know how this couldve happened.

[Captain Obvious]

Learning as you go is great. Take some time and at least read through the tune up and engine fuel sections of the manual. It will not only add to the learning experience, but it will also help you communicate here.

Not sure how to interpret your results with carb cleaner. Usually the typical reaction to a carb cleaner spray around leaks is an increase in the idle speed, not a decrease. Especially if you are running lean.

What do you mean by "new" carbs? None of these carbs are new at this point, right?