Back before electronic ignitions were the norm, a faster advance was considered a slight advantage in the 1/4 mile. A quarter mile was and is , run with the engine relativly cold. Often vac advance was locked out or removed (one more unneccessary variable for drag racing). Drag racing at that time was mostly class racing - Stock Eliminator.
I worked with a mechanical tech who played in that game. The secondary spring is needed for electronic ignition. He learned the hard way and passed it along to those of us who would listen.
Actually its not that big of a secret, but the magazine writers have never caught on. Read post #4
https://www.tapatalk.com/groups/racingfuelsystems/too-much-advance-at-light-throttle-t666.html#p5625
Here's a couple other guys who have run Stock Eliminator commenting on the subject. GTX John and 92b. What used to be done with dual points no longer applies with electronics even for drag racing.
https://www.forabodiesonly.com/mopar/threads/lets-revisit-timing.499590/post-1973619145
Some observations here on Slew rate
https://www.forabodiesonly.com/mopar/threads/ignition-box-retard-with-rpm.455065/#post-1972841635
The other thing the long looped secondary spring does is allow the vacuum advance to come into play at part throttle.
If the secondary spring doesn't slow the advance, then there is too much timing at part throttle with vacuum advance. Or you have to compromise the vacuum advance.
You're driving for a couple hours at 50 - 55 mph and a adding a little throttle for a slight grade causes a gurgling (ping). I got to learn this the hard way. But feel free to try it out yourself. Really no harm. Just annoying and less efficient.
