I have a Pontiac distributor I working on set up on my distributor machine right now. With new points ( heavy duty NAPA brand ) and a new condenser, the dwell is set at 32 degrees. At 6000rpm it will back up to about 29 degrees. Its a slow back off and doesn't start till around 4500 rpm. Below 4500 rpm, it is rock solid at 32 degrees. With the standard set of points, it won't make it to 5000 rpm without cutting out, the spring tension is too weak and the points start bouncing, yet the dwell is still with in range.
You have distributor issues if the dwell is moving more than a degree or two at higher rpms. Does the timing advance with rpm? Does it advance with the vacuum applied?
Also, when it back fires, is it tail pipe or intake manifold?
