[wilf leek]

Chopper - I know I am English, and thus automatically deficient in the ways of proper engines with 8 cylinders and more than 2 litres big, but I do know the difference between the light and heavy silver springs!! But it was a good thing to check.

In actual fact, I believe I have sorted the mystery. When my car was on the rolling road, it really wanted more advance at lower revs, in fact it would probably have been better with a vacuum advance unit. So I made up a special bushing, larger than the largest std MSD one, to restrict the total mechanical advance even more. Then I set the ignition at 35/36 degrees at 3000 rpm, and left the static or idle timing to be wherever it wished, In actual fact it runs out at around 22 degrees btdc.
The result of this, now that I look more closely at the MSD curves, is to bring all the advance in earlier, hence the results I am getting. Engine starts OK at this setting - no kickback, and runs just fine.
I might set to work now to lighten the arms inside the dizzy to trim it back a bit.
Thanks for your help.