If the one spring (call it the primary) is really a “light” one, it’s probably not original IMO. The use of that heavy spring (call it secondary) with the long eye requires more than a light spring to control advance as up to something like 4,000 rpm it’s the only spring controlling advance. Those heavy, long eye springs don’t start allowing the last of the centrifugal advance to start coming in until something like 4,000 rpm or even higher and probably won’t allow full advance until some ridiculous level like 4800-5000 rpm’s.
With a “light” primary spring the first half of your centrifugal advance swings in quickly at lower rpm’s and then it just stops when the weight pin takes up all the slack in the big secondary spring eye and the engine has to wind up to higher rpm until the secondary spring starts to stretch, allowing the rest of the advance to come in. So you have a 2 step advance curve with a plateau in the middle. It’s not a good set up. I believe Mopar used a medium weight primary advance spring to slow the initial curve down and shorten the plateau between initial centrifugal advance and later centrifugal advance. Either way that big heavy spring with the elongated eye is not a good performance set up.
As noted above, it would be a good idea to make sure the secondary blades are closing at idle when the engine is warm. I’ve found an AFB where the bent rod connecting primary and secondary blades on the right side was bent from age and use and would not open the secondary blades fully. I guess it’s possible that something could get out of wack and not let the primaries close at idle.
