Relationship between idle jets and idle mix screws Options

[era vulgaris]

How much can one compensate for the other?
For example, with larger jets and idle screws further in, could you tune a set of carbs identically to another set of the same carbs that had smaller jets with the mix screw further out?

I want to experiment with going a little leaner at idle and seeing how my engine likes it. I'm trying to decide if I should order a smaller set of idle jets or if I can achieve the same result by just turning the screws in further. Basically, what is the difference? Don't they achieve the same ends? Obviously there's a limit on the rich side because there's only so much fuel a jet will allow to flow. But if you're trying to lean it out, what's the difference between going to a smaller jet or just turning in the screw?

[r_towle]

I saw the thread, was not blind, just bored stiff staring at the screen all day.

They do make those spacers, but it really depends upon how hot things are getting.

It sounds like you have a list of issues.....and you may need to trace down more than one problem to make everything right.

I don't doubt that you have been looking at lots of things, but I would suggest you focus on heat, and only heat.

It runs good cold.
It runs worse after its hot.
So, what changes with heat.

To me, a few things come to mind.
Old distributors get really sticky and advance plates get stuck when hot, and to make it fun they get stuck in different positions, advanced, no advance etc....so look for advance plates that are stuck when hot...not a fun test but you will need to see how well it works cold, then try it hot...without getting burned.
Mine did this....it was 0.05 cents of grease, and my time to clean the distributor.
Found that after I replaced the entire fuel injection system.... (IMG:style_emoticons/default/smile.gif)

Valves.
Valves get longer when hot, so they will have no tappet clearance, or even worse they may be held open a hair when they are hot. This can make you have no compression, or worse an inversion...which will make it run like crap....
Btdt, check your valves cold, then see what they are hot.
Hot is not fun, but really a valid way to adjust valves....should be damn near zero, but not zero clearance... So when they are hot, the Valve does indeed close completely, but there should be just about no noise.
In my book, noises valves are happy valves, in aircooled cars.

Did a ton of work on the 911, still had a weird idle when hot....it would hunt.
It was the valve adjustment was too tight.

And fuel.
These engines get hotter when y shut them down. It's a heat sync.
On the 356 cars the issue was the fuel could boil, and by boiling it could go down into the engine, and create a hydro locked car...so much fuel in the cylinder it would not turn all the way over.. I have had to rescue one 356 at a show from this....we removed the plugs, got her running on three, then shut her down and got her going on four after we put the plug back in.
I was the youngest guy there, so I had to get dirty while being coached by my elders..
It was a hot day, show car, super tight new motor....