In the past, member have had excellent discussions about ignition timing as it relates to distributor advance and the various springs that speed up or retard the distributor advance curve. However, in these discussion I have not noticed examples of why a particular spring was chosen as it relates to the rate (speed) of the advance curve. For example, in drag racing, should a light race car use light springs for quick timing advance versus a stronger spring that lengthens the advance curve rate for a heavier car? In essence, I would like to know what general guidelines members can provide regarding spring advance depending on car weight or camshaft or transmission (manual vs. automatic) or whatever other variables you take into considerations when selecting a distributor advance spring. Any input about which springs work best in different applications would be great. Thank you.