Let me ask y’all this:
Seeing as my 390 in particular is a fresh build (roughly 5k Miles) what could be the chances the head gaskets could be at fault or even the heads? I know nothing about the internals or the guy who put the engine together. Could gaskets be on wrong? Could the heads be warped?
These are not GT heads... do the GT heads have cooling passages that non GT heads don’t?
Ethan, the GT heads are just passenger car heads, no different and not even really a "thing" The only reason many people refer to them as GT is the exhaust bolt pattern compared to the same head in a truck. They run fine and with work can make power, but they are actually the lowest performing, totally normal head found on everything, so GT are stock heads. Not to mention NO FE head has any different cooling passages and if you had the headgaskets on backwards it would overheat all the time, you couldn't drive it. If that IS the case, then maybe, but doesn't sound like it.
As far as yours overheating, to be blunt, I see this all the time. "I took off the engine driven fan and now it overheats"
You have a 300+ HP engine driven fan and replacing it with electric fans with tiny motors. Electric fans are rated for 1000, 750, cfm etc, but that is free flow. Unless you get a real bad-ass setup (Lincoln, Taurus, etc, and wire them to a big relay with a good alternator, you won't get there. In electric fan speak, you need 4000-5000 cfm puller, with good bypass doors to match the stock setup
In the end, we all like the cool factor of electric, but it's never cheap, and it's hard to beat a stock fan or the Flexalite fixed fans with the bent tips, flex fans are noisy and crappy, in the end, I'd go back to what you had originally, or I'd go deep in a real set of pullers.
FYI If you are really set on electric, look in Summit at the ready made sets for pickups, they pull 4000-5000 cfm and if you have the wiring to feed it, they work pretty well
As far as the ignition, if anyone's engine overheats
due to not enough initial timing and the starter cannot handle more, then the car needs a better starter/battery/etc along with likely a fan/pulley problem
The ONLY reason I would run manifold vacuum is because I couldn't run enough initial to dial in a very big cam for idle tuning. Basically you can start the engine then timing comes in for idle to allow you to close the primaries to stay on the idle circuit, that is a much different reason.
However in that case. I will also add, that I deal with this on early Pontiacs, manifold vacuum for a distributor is awesome at idle, and at WOT, but can screw with you in between. As you work the throttle in town, you often end up with it coming in and out as it drops and rises, it can feel weird. Not wrong, you can tune it, but can be odd until you get it where you want it. In my opinion, I stick with ported other than some very limited vehicles