It's very unusual for an engine to die because one screw is turned all the way in. But if the carb is really misadjusted or defective it can happen.
Usually when the screw is turned all the way in it just runs slower - and still should run smooth. That's a valid test. The "stumble point" is only about 1/2 to 1 turn out from fully closed (time? - 1 second?)
WHY? Each side of the carb feeds 4 cylinders on your V8. Look at the runners on the intake manifold.
The carb's left side feeds the 2 end cylinders on the left side, and it feeds the center 2 cylinders on the right side, for a total of 4. The other side of the carb feeds the other 4 the same way. Yes, there is some mixing of gasses in the plenum where it's open (sometimes,) but essentially they are 2 independent systems.
If you look at the firing order, you'll find those are every other cylinder in the firing order.
And they are also a balanced set.
If all 4 of those cylinders were to quit firing, the other 4 will still fire, and since they are every other one, and mechanically they are balanced, the engine will run fine, smooth, just not as much power.
If one side of the carb isn't working, and you shut off the other, yes it will die. And when you shut off one side and it doesn't run smooth, it shows that one of the remaining 4 has a problem.
We did not go into a deep explanation as to the how and why, we just needed to know the reaction. It's only 1/2 to 1 turn anyway, but it tells alot.
On here there isn't room or time to get deep into theory if we are to help. Just believe us - unless you think we are crazy.
I think we both have been on here long enough for you to realize I don't believe in throwing parts at something - guessing - I'm a believer in testing, then verifying, then if needed, replace. Yes, there are some that are the opposite, "replace everything in sight till it works."
I never ask anyone to use sophisticated test equipment unless it's absolutely needed, even though I own most of those things.
KISS is my byline.