Distributor Vacuum Advance?
If your car is driven on the street it will be spending 80-90% of it's operational time at light throttle cruising so it only makes sense to dial the vacuum advance in too.
Agree
Almost all street driving, with a street car, that might have 3.23s to 3.73s, is or will be, done at under 3000..... because in second gear, your rpm is about 2000@32mph, give or take 200 rpm for gearing. Most of the time you will be just cruising or lightly accelerating in traffic.
Without the vacuum advance working, your A/F mixture will NEVER finish burning in the cylinder. Instead of making peak cylinder pressure at the optimum transfer point in the crank's position, the pressure pulse will follow the piston down, and some of the fuel will remain still unburned. When the exhaust valve opens it will exit lazily and keep on burning in the exhaust system, destroying any scavenge signal that may exist in the header. Not only does this waste energy, but the engine is not making decent power, so you have to drive deeper into the throttle to maintain even your modest speed.
Try this;
In N/P set your idle speed to 2000 rpm without the vacuum advance connected, then read your Ignition advance. Next hook up the Vcan. Your rpm should jump up. Read the advance again. Finally tug on the distributor, and bring in more advance, until the rpm no longer rises. Then read the timing again. What you have there is the amount of advance that the engine actually wants at that rpm and load setting. What did your timing light tell you? Compare the final amount to the starting amount.
Don't forget to put the timing back to where you found it, lol
