So he says to use the manifold vacuum instead of ported vacuum (thats usually recommended). I think I understand why he says this but does anyone care to elaborate more on it? Oh and WTH is gas knock?
The reason he says to use manifold vacuum is it gives you more initial timing at idle. The more initial timing you can dial in and the car still run good without spark knocking (what he calls gas knock) under acceleration the better the fuel mileage usually is. The only problem is with a engine that has a much larger than stock cam (such as yours) it may or may not have enough manifold vacuum at idle to keep the vacuum advance pulled in so it'll idle erratic. With the cam you have I'd expect your car to pull 10-12" of vacuum at idle which is kind of right on the line. Wouldn't hurt to try. You can always swap it back if it doesn't work. If it works it might save you from having to pull the distributor apart to rework the advance slots
BTW: earlier you mentioned your other car and how the distributor caused it to "hunt". More than likely that's because the advance springs were too light. I ran into that problem back in the early 80's when I started tinkering with distributors. I've found using one light and one medium spring usually works better. Most street engines don't like full advance by 1200 rpm like 2 light springs will give you unless your running a real big cam that has low cylinder pressure.