[Hugues]

Much more, if the rotor is phased. Consider a random example - if timing changes 40° from 10° base timing to 50° max timing, the angle of the rotor sweep is half that (40/2=20°), and is on either side of pointing directly at the cap terminal (from 10° to -10° of aligned). On a 75mm I.D. cap, that's about 13mm sweep (±6.5mm each side of aligned).

You can have some pretty extreme timing if your rotor is reasonably phased: Rotor phasing (ignore the 'bonus' stuff at first, until the concept is solid, then it should make sense)

excellent write-up, i thought I knew how distributors worked...
Me thinking that i should instead buy a newer Bosch coil driven by my ECU and coil driver,
and let my distributor untouched, this way i don't have to change anything, not even lock the weights.
thanks ! learning each time i come here

[PSIG]

You certainly can, and why it's important with a very flexible ECM, to remember you have many options to choose-from that fit both the project and your brain best.