How will I know I'm where the engine wants with the timing? Sorry if it sounds stupid, I just want to make sure I get it set up correctly.
You use a vacuum gauge hooked to a source below the throttle blades of the carb so you are getting manifold vacuum.
Using the gauge, disconnect the vacuum advance if you hav one. You turn the idle down to a somewhat low idle rpm -750 800 rpm, then start advancing the timing until you reach maximum vacuum. You may have to turn the idle back down to keep the motor at a low idle as the rpm will keep increasing until you find the end of the upward curve and you stop gaining more vacuum.
Once this happens, retard the timing back down until you see the vacuum start to drop from it's peak. go back and forth until you find the lowest/highest timing that gives the mot vacuum at idle.
That is your initial timing. Your total timing is best found on a dyno, but most Mopars like 34- 36 degrees total timing. You will have to pull your distributor. I like to do it on TDC on the #1 firing stoke and weld up the slots near the end of the travel of the advance mechanism. Usually no more than 20% of the total slot length You can use a small chain saw sharpening file to reshape the end of the slots to match what it looked like originally and keep them even.
Re-install the distributor and test where your total timing ends up. you may have to do this several times until you end up at 34 to 36 degrees total with your initial advance set where you found the sweet spot for your motor using the vacuum gauge.
Once you are dome you then need to adjust your vacuum advance pod using a small allen wrench to turn the screw deep inside the hose nipple start out with it screwed all the way in and then slowly back it out until you hear a gas knock when you transition from light throttle to moderate throttle on the freeway. Back it off a half turn from there and try it again.
It's time consuming, but you only have to do it once.
Always!!!! hook you vacuum advance below the throttle plates, so it sees full manifold vacuum at all times. You will have to turn your idle down even more once its hooked up because it adds more advance at idle.
Once you open the throttle, the manifold vacuum drops, and the extra timing advance from the vacuum advance falls back down to the initial timing setting you figured out earlier with the vacuum gauge.
These number are magic in how they will optimize how your engine runs, but they will like not be what most usually guess at. Some people get close, but they have lots of experience and read lots of good stuff about this the internet.
I had a slant six that liked 22 initial and 32 total. It had twice as much power out of the hole when I was done tuning it this way and got better mileage, dramatically better drivability and ripped on top end. It was a nice little slanty tough.
