The hotter ignitions are more necessary on cars that were not originally forced induction. Volvo raced both the 240 and the 740 Turbo with the stock ignition, at elevated boost levels. On a 240 Turbo, something like the MSD 6 AL BTM would help at higher boost levels because you can proportionally retard the timing relative to boost. I used the Crane Hi 6 TR on my 83 242T. Holly and Accel make similar devices. On the 745T, there is a pretty good knock sensor. I still think the MSD (non retard model) probably helps a tiny bit -- just not enough to feel. Multi spark ignitions do tend to help older carb cars noticeably. The carb is not as precise a fuel delivery device as fuel injection, and the multi spark below 3000 rpm helps smooth things out and add power at lower rpm. Also, ignitions were not quite so strong way back and often had to be adjusted (points); converting to an electronic amplifier will help.

Philip Bradley