Only runs 40 Degrees advanced

I don't understand how a rich mixture changes the timing. Fuel is fuel and electrical is electrical. Educate me. If the physical components are assembled correctly- the cam is correctly installed, TDC on the balancer is also the piston at TDC (balancer is accurate), then I have to be thinking that we are getting a false signal from the timing light. I don't mean to insult your intelligence, but are you sure that you are hooked up to #1 wire? Does your timing light have an advance knob and is it set to "0"?