Demo Ported Vs Manifold Vacuum
Under a slight load, manifold vacuum drops. Ported increases slightly. Also, and you can try this, ported vacuum can be considerably higher (as Full Manifold Vacuum or Not This video hows the difference between Intake Manifold and Carburetor Ported Vacuum on a running engine. It also shows the Never Connect Your Vacuum Advance to Ported Vacuum! Settling the debate around manifold or ported vacuum for vacuum advance. ...