I have verified that the weights move and I have messed with the weights and I know it made a difference, but it's been too long since I messed with it. Im fairly certain I switched to using the heavier weights to smooth out the idle park to drive transition (400 rpm drop).
The vacuum advance is full manifold vacuum. Ive always had smoother idling motors with full vs ported. The crane adjustable vacuum can is set to pull 14degs. I had inital set to 16-18 to smooth it out. 12 was almost diesel like super rough and didn't respond to removing vacuum hoses. And yes I set initial timing without vacuum advance.
OK, I am not sure I am getting this correctly, so bear with me. You have full manifold vacuum to the vacuum advance. Your vacuum advance is factored at 14 degrees. Your initial setting at the crank is 16-18 degrees. If you take away 14 degrees of vacuum advance because that is what you get with full manifold vacuum, then your initial timing at the crank with the vacuum line disconnected would be 2-4 degrees - way too low.
Now if you have your initial setting at the balancer at 16-18 without the vacuum line disconnected and then you hook it up to full manifold, you now have 30-32 initial - waaay too much. Add in your mechanical advance in the distributor and you have yourself a time bomb just waiting to detonate itself apart.
You should set your initial at the balancer between 10-12 degrees and then bring in your mechanical and add the vacuum to that IF you plan on running full vacuum to it. (Initial + Mechanical + Vacuum Advance on full engine vacuum = Total advance)
You also need to know when Total Advance is in. With the ethanol gas, it should be anywhere from 2800-3200. Some will go as high as 3500 RPM, but this is something you have to play with using the springs/weights of the mechanical advance. Lemans guy will be able to answer better on this one.
Keep in mind that if you have an original balancer with the bonded rubber that these can slip and the marks will be off and setting your timing to them will be off. And, you want to make sure the correct harmonic balancer is matched to the correct timing cover and scale. People swap things around and they won't match, again, throwing timing off at the balancer so you cannot use it. I assume all your parts are still original to the 350. Did you happen to degree the balancer along with the cam?
Just for fun, disconnect the vacuum advance & plug the line. Set your initial at the balancer to 10-12 degrees. Take if for a test drive.
Now if the engine sounds crappy, with vacuum line plugged and disconnected, loosen up the distributor hold down bolt/clamp just enough so you have to use a little effort to rotate the distributor. Rotate the distributor right (Counter Clockwise - CCW/retard) until it runs rough. Note the position. Rotate it back (advance) the other way until it runs rough. Note the position. Now move it again counter clockwise until it runs nice and smooth. If it sounds slightly rough because you went to far, simply move the distributor back until it smooths out again. Leave it there, and take it for a spin. The distributor won't move because it is fairly snug, but can still be moved by hand. If you hear ANY
pinging under load, back off the gas as that is detonation and bad for the engine. Distributor is too far advanced and you can pull over and turn the distrib. by hand a small amount counter clockwise to retard ignition - test again. If it ran good on the first drive out, you can also pull over, advance the distributor (Clockwise) by hand a tiny amount, and try again. Again, NO PINGING
should be heard under load. If at a point you hear any pinging, you want to retard the distributor by turning it a small amount by hand and try again. Repeat until it goes away under load. Timing is now set regardless of your timing marks which you can check afterwards.
This is timing the distributor/engine by ear and how many do it and is how I do it to fine tune the timing once I get the initial set-up at the balancer. Just have to make sure you listen for the engine pinging and back out of the gas immediately and adjust the distributor - retarding it slightly counter clockwise.
Now if you want, hook up the vacuum advance to a ported
source on the carb. It is my understanding that the Crane vacuum advance is not adjustable with regards to vacuum, but rather, to how quickly the 14 degrees comes in, so keep that in mind - you will always have 14 degrees total and that cannot be changed, only the speed at which the 14 degrees kicks in.