vacuum advance

I know it came stock with a manifold vacuum source, But I wasn't sure with the edelbrock set up about which port to use. I think I will try the manifold port tonight.
Set the timing to 14 btdc with vac disconnected. Then hook up vac.It will probably increase the rpms a bunch when I hook the vac up. I guess I should then adj carb to get the rpms back down...That's where I get confused because then doesn't the timing change with rpms? How do you get the right timing and the right rpms at the same time?
Maybe I should take a class in auto 101 how to set timing.