Distributor Rebuild Question

If you use the FBO plate with a correct 340 dual point for the purpose of increasing the initial timing, then you can, and should, bend the secondary spring perch out. The secondary spring loop should contact at approximately the same rpm as it does now.

How it works is explained in another thread, but basically the secondary spring contact is based on degrees of advance. If you're going from say 5* initial to 15* initial, then the secondary spring needs to be adjusted the equivalent of 10 crank degrees to be effective.