Not really. As far a base timing and the addition of mechanical advance to that is "enough" by itself to gain max horse power and good overall engine performance. How fast you bring in the mechanical advance and how much you bring in varies with any given set up. The basics are 32-35 degrees TOTAL advance at some given rpm and that's it, your done. Vacuum won't have any impact at all on starting the motor, the only factor there is your base timing. There is such little vacuum available under WOT (wide open throttle) as to render the vacuum advance unit inoperable, same thing when you are cranking the motor to start it, no vacuum signal is present.
So why run a vacuum advance at all? A couple of reasons I do it. #1 is for better mpg, which means more RANGE in miles per tank of gas. #2 is a better overall idle speed, it can be smoother with a properly tuned vacuum signal, or not, depending on the cam, carb's, etc. #3 it helps or even flat out eliminates "run on" with engines forced to run a relatively high idle speed due to a wild lumpy cam. The vacuum advance helps to smooth that rough idle and allows for a lower idle rpm. This in turn allows the carb butterflies to be more closed so the carb doesn't suck up "air/fuel" after the ignition is shut down, thus preventing the "run on" or "diesel" problem some engines have when hot and a fast idle speed.
Under LIGHT LOAD conditions, think cruise rpm, flat land, steady speed, you can have a total advance amount of around 45 to even 50 degrees! Say 35 total of base plus mechanical advance PLUS another 10 to 15 of vacuum advance. 45 to 50 degrees advance will certainly damage your pistons and blow your motor IF that occurs under "load". But as soon as you "step on the gas" or put the motor under "load" the vacuum disappears and your back to your original 35 degree total. It's a kind of "fail safe" for running extreme advance timing, risky though, get it wrong and you WILL damage your motor. Get it right and it's sweet. Most engine builders won't take the risk of to much advance (and they probably never use starter fluid either).
