Having said that;
OP
rev up your engine, in Neutral, until it the vacuum levels off. Whatever the rpm gets to, you can consider that the lowest efficient cruise rpm of the combo, in it's current state. My guess is that it will peak in the range of 1800 to 2400, depending on your cam.
Say it peaks at 2200.
Now, without regard to the numbers, keep the rpm at 2200 and just keep advancing the timing until more advance does NOT produce more rpm. Now read the timing at that 2200rpm. Write it down, then put the timing back.
Now, my guess is that the number will be in the range of 50* to maybe 56*. Whatever you read is what the engine wants. How are you gonna give it to her?
Your Vcan is worth what? Maybe 12 degrees?
Your idle-timing is what? Maybe 18*?
Your centrifical, by 2200, is bringing in what? Maybe 10*?
for a total of 40*?
How are you gonna stretch that to 50/56? If you don't, your cruise-timing will be seriously retarded; and your fuel-economy will be seriously lacking.
You can modify your Vcan to in the range of 22/24, so from 12, let's say you get an extra 10*, so now you are at 50* and on the lower edge of adequate, but could be still 6 degrees or more, short of optimum.
Can you get it by increasing idle-timing to 24*? Or by increasing the rate of the centrifical? Well maybe; but if this causes detonation under Power, then no.
But increasing your Cruise speed to 2400, might get you 2 or 3 degrees of centrifical, and now yur up to say 53 degrees. Perhaps that is all your engine wants.
Go back and repeat the cruise-timing test at 2400 and see.
Happy HotRodding [/SIZE]
