It really doesn't matter if you use one port, two ports, or no ports at all- - - - -the vacuum advance will seldom, if ever work. There will be such a low venturi velocity and such low manifold vacuum that the only time you'll get any movement of the advance will be when you're coasting downhill with enough throttle opening to expose the port in the throttle body that connects with the advance tubing. As soon as the vehicle starts to accelerate on a straightaway or even a slight uphill, the intake vacuum will be so low that the advance won't operate. Just plug the ports, forget about the vacuum line, and try to adjust the total advance for the best performance without using the vacuum advance. Problem solved, more or less!
Jerry
