Originally Posted by Gen1dak
If the idle mixture screw adjusters have no effect when being adjusted, sounds like you have a carb problem. The engine should not idle at all if totally screwed down. A setting of about 1.5- 2.0 full turns open should be fine.
While a failing ICM doesn't typically cause a "miss" it is possible that it's failing, requiring time to cool off to run again fits that profile. That will get worse and eventually fail. Also, the ballast resistor needs to be replaced (white ceramic----brittle, delicate....don't over-tighten) on firewall near ICM. Fortunately, they're $20 bucks each, give or take. Blue ICM not uncommon for aftermarket, have had them myself. As the production of these things moved the China, those in the know always kept a spare set in the glove box. Just don't last like in the old days. If you get a good one, it will last years.
Another possible cause of the miss could be a little deeper in the ignition, meaning the distributor (single pickup or dual?) Could be a worn distributor shaft bushing in the block causing a wobble that's dropping a cylinder, but that's something to consider after everything else has been dealt with. You typically see that on very high time engines. It can manifest as a low rpm miss that improves as rpms rise.
It sounds like you're finding the basic issues on your own. It needs a tune-up. The carb is still a concern. Funny how on these relatively simple setups (compared to today) problems can still be difficult to ferret out.
I looked at the dist. and rotor/cap, everything looks good. I do wonder about the ICM. The ballast resistor is something I forgot about, but will be replacing.. The current one definitely looks crispy.. Since the ICM is only $23 I'll be replacing that as well..