"Pinging" could be timing. You say you have tried different settings. That should have had some results that you could hear. It's called spark knock also. It can be timing related or spark plug related.
Also the sound is called detonation/preignition caused by lean fuel mixture (carburetor) ........ or overheating/exhaust leak.
Tune it up with points, plugs, condenser, cap and rotor, and plug wires (all the cheap and easy stuff). Tune ups don't waste money. If a person has tried and can't find it and does not have equipment/Hot Rod Jerry type experience, the first thing is a tune up so as to start with a baseline of good electrics. If you can't install and set point gap accurately, find someone who can. Tripple check the gap after tightening screw by moving rotor on and off the lobe.
Then time it per the book. With slight tweaking. Then move to other causes mentioned.
Be Aware: Sometimes the sound you hear is NOT pinging. Especially if it runs good and does not overheat. Especially if you didn't get any results from turning dizzy back and forth. The sound can be an exhaust manifold leak/exhaust connection leak, a heat riser flapper, tappets, rod knock...........coins in your pocket, false teeth.
GET A STETHOSCOPE...or a broom handle. Listen at valve cover, all around on the block, each exhaust port, the pan, the dizzy, the draft tube, water pump, fuel pump.....
Good luck and let us know what you need or find out.
