Vintage Car

i put a new street 600cfm ontop of my 383 magnum. i was tuning it and trying to tune the two a/f needles. i was tuning it like this...turn right til the rpms drop noticably, then turn back left til max. rpm is reached. i am doing it all by ear cause i have a 69 charger with a 727 witch means tic-toc-tac(clock instead of tach) it was working for me by listening for the rpm raise, but then it stopped sounding like the rpms were raising when i tried tuning it again allittle while later after i adjusted the float level.. i seated the needle and still no rpm drop??? anywho... i have to go somewhere tomarrow so whats wrong and how many turns out from seated could i put it at as a rough tune, so to speak, so i can drive it w/o it leaning out or flooding??thanks..