[Gaz64]

The purpose of Holley's bypass valve is the same as a Barry Grant Idle-Eze, or any other adjustable "vacuum leak".
You should set both Primary and Secondary idle speed screws so the transfer slots resemble a small square as viewed from the bottom of the carb.
At that point, the bypass valve has enough range to have almost any engine idling at respectable speed.
Back off your idle speed screws, open the primary side 1/2 turn, secondary side 3/8 turn, and the mixture screws at 3/4 turn out. Bypass valve in the middle of it's range.
Warm the engine up, adjust the mixture screws 1/16 turn either way, monitor engine vacuum and rpm, monitor ignition timing, adjust bypass to bring idle speed to near target, adjust mixture either way, depending on what the engine wants. Highest vacuum, then check AFR at idle.