340 with edelbrock heads overheating

That carb should start with 2 1/2 turns out from completely closed ie bottomed out in the bore. Warning though the 800 AVS is very thin in that area so don't tighten the idle mixture screws too much as they can can punch through. If the idle mixture screws do not work you have a problem
i must have another vacuum leak somewhere. that would explain why the idle mixture screws do nothing,