I don't know that I have watched rotation with the engine turning over. But I have figured out how to tell if the distributor is correct for a small block or big block. I have also tried a second distributor. Swapping the coil wires made the engine run better while the weird timing light readings continued. Now I'm more thinking I'm not getting noise free pickup. I have Spiral Core wires and the wires are a little close together. I haven't really started those checks yet : moving wires around, moving the pickup around, clamping on another plug wire. Maybe even trying some RF shielding of some sort. My symptoms include a strange move back to the initial timing, which may indicate a reset of the timing gun. This idea came from another site where a guy was warning of interference from racing wires or other non - stock wires.