Holley Idle Screws Not Responsive

Most likely the primary throttle plates are too far open and are exposing the transfer slots. This happens when an aftermarket cam is used and the idle screw needs to be cranked down for it to idle. There are two resolutions:

A: Not enough initial timing.
B: If you have dialed in enough initial, Under the carb, there is a set screw that can be adjusted to allow additional air into intake. This set screw cracks open the secondaries. Aftermarket throttle plates like the Quick Fuel have this adjustment on top which greatly simplifies tuning.

How much initial timing are you running, what cam and what compression? This information will help us help you. :)