i am not there so this is difficult. plug off all vacuum coming out of carb and intake, or at least make sure none of it is causing a leak. turn the mixture screws all the way in, then back out 1 an a quarter turns. start the car. adjust idle speed to specs (or best you can by ear) with choke open and engine warm. for automatics, adjust with car in drive. dont worry about the choke or the fast idle yet. turn mixture screws clockwise one at a time until rpm drops, then back out to position before rpm drop. readjust idle. repeat, turning mixture screws whichever way gives you the best idle (when in doubt go lean) if you have a vacuum guage, use it with the mixture screws to obtain highest vacuum. you should have 18-20psi of steady vacuum. verify ign timing. repeat procedure until best vacuum is achieved. once you know the carb is set right, your vacuum problems may be easier to find. i've heard holleys have float adustment problems. i know nothing about them, they should be set correctly from the builder. an easy way to find vacuum leaks is to spray carb cleaner around base of carb, hoses, and intake, if there is a leak, idle will change. i dont think adjustment is your problem, but it's a good starting point. i think the "ported metering block" is the vacuum block coming out of the manifold with hoses for different functions. if this thing runs fine until you hook up your advance, there must be a leak in the advance line or diaphragm. but it really shouldnt be drawing vacuum there until you accelerate, as ray just pointed out (q-jet or holley)which is why i suggested adjustment.
