The 8388 RTR distributor is shipped with 2 heavy silver springs. That is the slowest curve possible. The engine would likely have to go to 4000 rpm with the blue bushing.
Unlike a real GM distributor, with the MSD going to have to see what RPM the advance begins. heavier springs will delay the start even though they may be the what is really needed from 1600 rpm up. So these need to be tweaked like @midnight340did
But without a tach its all a wild goosechase.
