260z round top conversion: a couple questions

[Cooper260z]

Yes the second vacuum port on the manifold broke, I tried filling the hole with epoxy to seal it but that’s where we’ve found a vacuum leak when spraying brake clean in the area. 
 

I noticed that the linkage isn’t going all the way “home” I’ll say, and isn’t lining up with the service idle adjustment screw but I haven’t figured out why yet. I hadn’t noticed that connection but being bent before, it does look a bit tweaked, I’ll check that out. But this is the correct (I’m pretty sure) linkage for a 240z. 
 

With the flat tops the car did run quite well. I just noticed a few hiccups that I decided we’re likely carburetor based which is part of the reason why I was making the switch. So yes, using how the engine ran with the flat tops as a baseline, it should idle and drive fine. Maybe the tweaked throttle linkage is the main issue, I suppose that could explain the high idle but not the sudden idle jump and climb I don’t think. Also doesn’t explain the extremely low idle I don’t think 

[Cooper260z]

Alright, so this piece of linkage that connects to this bar is what was keeping the linkage from returning all the way. I’m not sure what this mechanism is for yet but clearly these linkages aren’t completely compatible with each other. 
Also I’m not sure exactly what order these flats are supposed to go in, maybe that’s my issue. 
 

But disconnecting that linkage fixed it! So I guess the reason that it was idling at sich high rpm was simply because the throttle was being held open... who woulda guessed. So with that detached the car will idle and be responsive so I can try to dial the carbs in and fix some other issues I can already see!

[Mark Maras]

 Concentrate on the float levels (primary mixture adjustment) and balancing the carbs first.

[Cooper260z]

Thank you @Mark Maras I will after I plug the air injection inlet so that I can concentrate on something other then the large exhaust leak in front of me. 
And while I wait on that, I’m looking at the linkage to this diaphragm. (That wasn’t meant to sound snarky or rude, if it did I apologize)
 

So, I got the linkage from the l24 which I now see is significantly longer. Is this the proper configuration? Suspending the adjustment screw on the front carburetor?

[Captain Obvious]

That vacuum servo that is giving you troubles is called the "throttle opener", and it's job is to hold the carbs open a tiny bit under very high intake manifold vacuum conditions. Essentially it is supposed to prevent the manifold vacuum from going above a certain level. It's in the same category as the anti-backfire valve.

And to answer the question about the linkage... No, that adjustment screw is not supposed to be floating in air a half inch away from the linkage. I assume that it's all caused by incompatibilities between the 260 bits on the balance tube and the 240 bits below.

Last answer... Yes, that is a round top style piece between the two carbs.

So for now, you can just leave the throttle opener disconnected and get the car running well. Then once you're over the  basic hurdle, you can get yourself a round top balance tube and throttle opener maybe.

[Cooper260z]

if I can get a hold of the 240z linkage then I’ll use that balance tube, but I do have the 240z throttle opener if it would make a difference but at face value they seem the same.
I feel like a bit of a bother at this point but do you know the correct way to attach the throttle opener linkage? The only way I see to attach it leaves that adjustment screw linkage piece suspended independently. Or are you saying that there isn’t really a way to do it because of my amalgamation of parts going on here? 

[Captain Obvious]

I'm saying that I don't remember the exact locations of all the parts involved and it's possible that the throttle opener may be mounted lower on the 240 balance tube. If that's the case, the throttle opener device itself may be identical between 240 and 260, but they may have put it in a different spot between the two.

Same goes for the throttle stop you're hovering above on the balance tube. That little stub of throttle linkage may be significantly different between the two. I just don't remember.

I know lots of people have done flat top to round top conversions and have overcome these hurdles and I bet there are pictures out there on this forum that would answer some of those questions.