Using vacuum gauge to tune engine?

AJ/Forms
Thank you for all the advice and suggestions. If I’m understanding most of what you said. You’re saying first get rid of the rocker clatter? Is that usually accomplished by removing all the lash or slop between the rocker & pushrod when dealing with hydraulic lifters?
Then when I can see the rpm of the engine at idle and listen more carefully. Then judge the proper adjustment by slowly turning the distributor to monitor the change in rpm. When you are saying set the degrees BTDC at idle is that when 30 degrees is not uncommon? Is that because the more high performance the engine the higher BTDC it likes at idle? There are some things that are beyond what I understand so I apologize if I don’t entirely understand. Then proceed to adjusting the idle screws and then setting the air/fuel mixture screws. The mixture screws synchronized I get but the work on the transfer slots I don’t understand demon carbs well enough to know how that ties in?
Carl
P.S. What is a v-can?