Wow, thanks for all that information. You of course now have my head
spinning. I have just been going through the advance curve suffle on a
sports car of non-British origin. The original distributor curve was
apparently quite special, with lots of advance upfront, staying steep for
30 degrees distributor advance (35 total with advance set at 5 at idle).
The 40 year old springs are no longer available, and the one guy who
rebuilds them with springs as close as possible charges $200. I've been
looking at alternative distributors and their curves. They are all so
different, some straight, some bowed to the left (factory), some dog
legging to the right before up some more, none with the 30 degrees
distributor advance but the factory one. I fortunately ultimately found
why mine was not advancing and fixed it. So, I'm ok for now.
But, given all those factors in what makes up the correct curve, how
exactly do they figure it out? And, is there any reason to believe that
the various car manufacturers actually did this for each engine? Or took
whatever was close based upon some theoretical belief of what their
particular engine would require?
Jay
1963 Sunbeam Alpine, dual Webers, high flow head, mechanical advance
distributor with unknown advance curve.
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