its running at 1000 rpm still gets hot and back fires.
What kind of carb do you have, and how do you have the mixture screws set? I have seen times when carb mixture is way too lean...makes it run hot, will make headers hot, and can burn pistons, and valves! If it's a Eddy, try 1 1/2 turns out.
Timing...instead of trying to set it, with the engine running, your better off getting it pre-set.
Pull all the plugs, so engine is easier to turn over, by hand...that's a socket on the crank bolt. Turn the engine until the timing mark is at 0, on the tab, and 'feel' with something through #1 spark plug hole, for the top of the piston. Should be right there. If so, then turn the motor 'reversed', at least a quarter turn. That's to get slack out of the timing chain, then rotate in direction, to the timing mark you want. Stop.
Pull the distributor cap, and look at the rotor...should be 'just coming up to' #1 plug wire. If going through this, something doesn't fall right, something is off, and it needs to be found.