First, I don't get why there would be this kind of thermal expansion that would open the throttles? First time I've heard of that?
All I can say is, my linkage doesn't do that BUT that's not what I want to say here.
The throttle linkage in a Pantera with multiple carburetion, and therefore IRFI, should have a VERY light feel to it and work VERY free and easy.
In fact when you have it right with Webers, it will work with just the return springs built into those carbs much lighter than the original 4v Motorcraft carb does.
Mine is so light it feels spooky. Almost like it isn't connected at all?
MTS commented that his hangs up.
In the past there has been discussion here involving the Pantera throttle cable. Apparently some have run into difficulty with it to the point of verbally trashing it and physically as well?
This business of having to "blip" the throttle to idle the engine down is a symptom of at least the Pantera cable not operating correctly.
What I found on my setup is that if you examine the way the throttle cable is routed, when you switch over to the "Weber" manifold (and probably most of it's variants) that the original cable isn't flexible enough to make the turn and go under the distributor to get to the universal throttle wheel, and it NEEDS TO BE. Using the Weber manifold with the center linkage tower, there is no other way to make that linkage work or the cable to line up with it unless it goes under the distributor.
What determines that is the type of linkage you use to connect the throttle to the left and right banks. If you route the cable to a side bracket like you might on a Mustang, you still will have the issue of lack of flexibility of the throttle cable because of the internal tube. The turn up over the valve cover would in fact be more severe so most "techs" have decided to use the under the distributor routing.
IF you disassemble that cable and remove the internal 3/8" steel tube on the carburetor end (looks like a 3/8" steel fuel line) reassemble it, then the cable will not bind from kinks and/or strange curves that you have attempted to put into it for routing purposes.
The entire cable will work lightly and freely at that point, which you will feel with your foot at the accelerator pedal AND the installed return spring in it will easily operate all of those carburetors, returning them effortlessly to the stop screw settings that are installed on the carbs OR THROTTLE BODIES.
The additional springs that you see on my setup (Moroso) are there for safety reasons as well as satisfying race track requirements of having a second return spring on the throttle. They aren't necessary to close the throttles at all.
They are also placed there so that the track tech inspectors can easily see them. Concealing them from view in any way is not a good idea for this reason alone.
I am also suspecting that this, the throttle cable issue, is involved in the original issues with "thermal expansion" on this particular throttle set-up. It may just be that the center tower on the original Pantera Weber manifold also eliminates that expansion issue since it creates enough play to eliminate a single rod from left to right from expanding? Maybe the one piece manifold casting also braces the engine from the valley contracting with individual left and right manifolds?
Apparently from what I am seeing this throttle cable business (and fix) is a well kept secret?
In fact, I was asked about this by another Pantera "tech" that was working on a Quella built fuel injection system just like this MTS one. It had similar problems of returning to idle. He was blaming the CPU for the issue. He changed from a Haltec to a Fast, constructed and installed a vacuum "manifold" system, built a new wiring harness and installed a pressure sensor in that vacuum manifold to fix it but I think it is mechanical, not electronic. An expensive fix for a simple problem with a simple solution.
He says it runs better now, but still not right. Sure. He didn't fix the throttle cable issue. Stubborn.
So I thought at this point, this comment was appropriate to the issue at hand?
Mike, while everything is open, check this routing of the throttle cable. You will see it from inside of the cabin with the engine cover off. You need to disconnect the throttle cable from the rest of the linkage and test it for freedom of travel.
If that cable IS hanging, there will be no doubt. You will feel it right there.