There are a couple of problems to your adjustment procedure. The mixture screw only affects the mixture at idle, so unless you're idling all the time, you've done nothing to affect the fuel mixture while driving. That's the function of the float level, main jet, and power valve, and the float level is the only thing that's easily adjustable. Using the vacuum gauge is a good way to set the idle mixture, but here's a better way to do it. With the gauge attached to full manifold vacuum (The wiper port is a good place), turn the screw in clockwise (lean) until the vacuum starts to drop, then turn it out (rich) until you get the highest vacuum reading. If you get things too rich, the vacuum will drop aagin. Once you've found the best vacuum reading, go 1/8 turn rich, to help the tip-in, where the transition from idle to part throttle is made. The float level is very critical to a good tip-in, even slightly too low will create a flat spot. If the spark plugs are getting sooty in normal driving, you need to work with either the power valve or the main jet. Make sure the power valve piston moves freely, and the ball in the power valve is sealing well, and reduce the size of the main jet slightly if necessary. A lighter-weight spring under the power piston will delay the power valve opening if necessary. Good luck!
Ignition timing- - - - -If you want to set it by ear, do so on the road, by listening for detonation, that light rattling noise under load, like climbing a long hill, and retard the timing a degree or so at a time until the rattle stops. Don't worry about the vacuum advance, it goes away when you load the engine. Its only function is fuel economy at light throttle.
Jerry
