read what d hearne said .. the screws on the side of the metering blocks are the idle adjustment screws which only effect the idle mixture .. you want to get them adjsuted to put out maximum vacuum at a given idle rpm or to maintain the highest rpm once warmed up .. that means they are adjusted properly, then adjust the idle speed to speed or slow it down. shouldnt take more than 2 full turns out on each side, usually between one and one and a half turns on a holley/demon. if its leaning out on the top end(read the plugs) then you need larger secondary jets, if its leaning out between 1000-3000 rpm under partial throttle then its the main jets .. also try different timing curves most people with carb problems just have mistuned ignitions .. and try different vacuum advance springs if the secondaries are vacuum operated.