[PeteF]

If you have no vacuum advance on your distributor, then both of those ports should be capped. If you do have vacuum advance, then it should be connected to the lower port, which is full manifold vacuum. This will give you vacuum advance at idle, which will allow you to lower your throttle idle screw and provide a smoother idle(due to more advanced ignition timing). The top port is timed vacuum, which is an emissions port, which provides vacuum advance only at higher throttle conditions(for emission controlled engines). I suspect your problem lies elsewhere. The adjustment screw on the vacuum advance diaphragm can be turned out (CCW) to make the secondaries open sooner. Sometimes they are set for a heavier car and open too late or not at all. Also, recommend you check ignition timing to specs. The Quickfuel or Holley websites may have more info. (Holley bought out Quickfuel). Good luck.