At low rpms, the conventional points-type ignitions willl be close to the HEI in terms of energy output. But as rpm's increase, there is less time available to charge the coil, because of the ballast resistor which is used to limit max current at low roms. At high rpms, 2.5 amps or so is all that can be achieved, as quoted earlier. A typical GM points coil is around 6-7 mH. So that leaves us with about 22 mJ of energy at high rpms.
