Can't see the vacuum changing by ignition timing, unless the timing increased the rpm with the throttle plates still closed, but you would lower the rpm again with the idle screw.Valve timing yes.If you're getting your total all in by 2200 rpm and your initial is 12-14 you most likely have to put stronger springs in the mechanical advance. You should have your mechanical max out around 3000 rpm. Your old springs may be worn out or just too light.
Rohrt, is that an SD Performance Stump Puller? If so it's the same camshaft I have. I get 12-13 in. vacuum max . Some do have starting problems with a high initial timing,. That can be cured by modifying the advance rate to get the max at the rpm desired with a lower initial, then increase the vacuum advance to get the higher timing at idle. Some have used a hold off switch to allow the crank to start rotating before the ignition is powered, a relay can be used as well I don't have a problem with 10.5:1 but 12:1?
Yes its the SD cam. As I mentioned mine is on a 114 LSA instead of the 112. I get anywhere from 13-15 in depending where I set the idle. The idle is very smooth and I can lower it down to like 650. I usually keep around 750-800.
You can play with timing forever trying to figure out what works for you. I usually say to work backwards. I think this was already mentioned. Shoot for the most power at WOT. This is usually 36 deg with Iron heads and 31 deg with aluminum heads much depending on chamber shape and quench.Then you have to see what your left with on the initial. It might be way to low. 12 is usually the mark most shoot for. If you use a HEI you have to find a center plate and weights that will work for you. If you use points you can do what I did and put in a set screw in to limit the amount of mechanical advance.