Mustang_Geezer":21i79gj7 said:
A shorter advance curve may help in your situation. This would allow More initial timing which would increase idle speed, thus permitting you to CLOSE the throttle further which will bring the vacuum UP.
To clarify my earlier statement, with a long overlap period at slow speeds there is a fair amount of flow going to the wrong places; some intake mixture ends up going out the exhaust, some exhaust goes up the intake; lots of bad stuff happening. This results in lower volumetric efficiency and lower cylinder filling which means you have to open the throttle wider just to keep it idling. This wider throttle opening causes lower vacuum (all else being equal).
Advancing the static timing will help, but you don't want the centrifugal advance coming on at its present rate or it will ping. Heavier springs/lighter weights would solve that. And the advance would need to be limited to prevent over-advance at the top end.
All in all it is a rather complex issue.
Have fun,
Joe
