Thanks for all the replies, everyone. I’ve got a few updates to my situation, I’ll try to respond as I can to all those who have offered suggestions. This is going to be a long one...
I think everything that’s happened to the car up until now (cutting out, pinging, that knock I described in the long post, also the absolutely horrible gas mileage I for some reason have neglected to mention until now) is related to fuel delivery pre-carb. I took a while to do more research and drove the eagle for a while and the clunking got worse to the point that it would cut out repeatedly on acceleration, which also happened to feel exactly like what it did on the highway. I bought some more testing equipment (I’m only 19 and don’t have much money or experience, so I’m taking it slow and careful so I don’t mess up), hooked a fuel pressure gauge up behind the fuel filter just in front of the carb.
The gauge flickered rapidly between 0 and 2-3 PSI when the car ran, and didn’t seem to change when I throttled her up. Although, the gauge sprung a leak after just a few minutes of me starting to read it, so I’m not sure if it was too accurate.
Nevertheless, I decided to start fixing a few things regarding my fuel system, mainly under the hood. Replaced the filter, replaced a few lines, bought a Schrader valve tee fitting (for easy fuel pressure testing in the future) and installed it inline after the filter - also got rid of the weird curvy hard fuel line between the filter and the carb. I also disconnected the inlet line on the fuel pump and blew compressed air back down into the tank. Sounded reasonably clear, but doing that procedure brought a question to mind:
Is there a filter between the tank and the mechanical fuel pump? If not - this car sat for about a year, maybe two, without being driven while it’s head gasket was blown. I drove it on bad gas for a little while because I didn’t have a choice, so if there’s no filter between pump and tank it’s possible that the fuel pump has swallowed some gunk and gone mostly bad. I know there’s supposed to be a pickup sock in the tank, I’m just not sure how it would hold up to age... Given the reading from my questionable fuel pressure gauge, the fact that the old fuel filter still seemed to be good, there didn’t feel to be anything stuck in the line when I gave it a good squirt of compressed air, and I couldn’t spot a fuel filter under the car... I’m leaning toward the pump being my issue. It looks original, and if it IS bad, I could’ve just been leaning out this whole time and not known it until the car started sputtering.
I’ll work on the car some more tomorrow, and after I can get the fuel pressure stabilized I’ll work on resetting the carb to IS-12E standards.
ANYWAY, onto the responses.
Did the 86 year have a weighted mechanical advance in the distributor? I've seen the weights stick and cause an incorrect advance.
Also if you are still running the Carter and presumably the computer you cannot adjust the fuel mix without the computer cancelling it out. Is the stepper currently set to full-rich because either the O2 sensor is detecting or is stuck in a hard-lean condition?
I’m not sure if the advance is weighted, but a few months back I did pull the distributor off, clean the advance mechanism, and verified its operation. Not sure if it’s proper though.
I am still running the carter WITH computer, BUT I have adjusted the fuel mix and it definitely makes a difference. I can hear the car’s idle change when I fiddle with the screws, and after I found out that I didn’t have one of them set right I adjusted it and the idle went from choppy and low to a better sound and feel. I’m not sure about the stepper motor, how to tell what it’s set to. Carbs are still new to me - the oldest thing I’ve worked on before this is my ‘89 Cherokee, and it has port injection. Waaay simpler.
A lean motor runs hotter and a mistimed motor can run hotter (either retarded or advanced).
I’m pretty sure I’m running lean. Would LOVE to have a method of actually checking if I am or not, but I’m not sure how. However, I’m only running 12 BDC at idle, and the advance bumps it higher depending on RPM’s. I don’t think that’s far enough off to cause issues related to mistiming. I do have misses on different cylinders from time to time, however.
Re the overheating; wonder if someone put a V-belt water pump on a serpentine-belt engine (or vice-versa). Pump would be spinning the wrong way then. Wouldn't be the first time I've seen that.
If the pump were spinning the wrong way, wouldn’t that cause a MUCH higher temp? From the readings my infrared thermometer has been giving, I’m running 160-190 at idle.
Come to think of it, I am having issues to get my heater to blow warm even after I bled my system, and there was a fair amount of residue in the line leading to the heater core... Too much for my comfort, especially because that’s a brand new heater core.
EDIT: I forgot to mention this, but I can actually feel the fuel line pulsing when she’s running. Not sure if that’s normal or not, but since the gauge flickers too I’d take that as a sign that my gauge isn’t bad but that there is in fact a delivery issue. There doesn’t seem to be a pressure regulator anywhere either, which is odd to me - but I guess that since this isn’t exactly a high-pressure application like fuel injection is it isn’t really necessary.
EDIT EDIT: Last edit, I promise! I’ve heard some rumors about 1986 eagles having the option for a crappy transfer case, or something. I took a look at the identification plate on mine and I have an NP128 AM. Is this the good kind, or the bad kind?