You're Welcome.
Be sure to lubricate the Needle Assy O-Rings with chapstick or something before screwing it into the bowl.
When reattaching the front and rear fuel bowls, 1st overly shorten the Accelerator Pump Arm Screw with the spring on it. This prevents the Pump Arm from 'displacing' the Bowl downward when mounting the Bowl and Metering Block to the Main Body. I stand the Holley vertical up on end when installing fuel bowls. Install the 4 Bowl Screws but do not fully tighten. The Bowl & Block assy can be 'wiggled around' in place with the screws almost tight. "Centralize" this "slop", "midrange it" before then tightening the Bowl Mounting screws evenly in an "X" Pattern, Firm Hand Tight with a NutDriver. Beforehand for the gaskets I get chapstick on my finger tips and liquefy it between the fingers and then apply it to the gaskets as only a thin film, avoiding any amount in the gasket holes. "Midranged" Bowl mounting location promotes proper Accelerator pump geometry. The bowl can be "mis-mounted" a considerable amount up, down, or sideways, due to the "slop" which adversely affects resulting Accelerator Pump geometry.
Imho the Secondary Idle Opening is whatever it want's to be.
The driving factor is the Primary Idle throttle opening must be correct relative to the transfer slots.
Primary is set on the bench, then not changed, unless closed further, which is unlikely.
Then once on the car all idle speed adjustments are made by way of the secondary idle speed screw.
Valve Adjustment, Initial Timing Advance, and Advance Curve must all be set 1st and not changed,
as changes to any of those will change the carb idle settings.
The Vacuum Secondary will also operate considerably better with sufficient secondary Idle opening.
The Vacuum secondary diaphragm is acted on by Venturi Vacuum, not manifold or ported.
Venturi Vacuum pick up ports are high up in the main body venturi bore just below the pinch point
and it has an opening to both the Primary and Secondary Bore on the passenger side.
So airflow on the primary side creates a venturi vacuum signal, BUT it must 1st overcome the "leak"
of the same common passage opening also on the Secondary side which has minimal to no air flow
creating basically no secondary Venturi Vacuum signal IF the secondary butterflies are almost or basically closed at "idle"...
Cracking the Secondaries more at idle increase "idle" air flow through the Secondaries,
which increases secondary Venturi Vacuum Signal, which reduces the "leak" the Primary has to overcome,
therefore resulting in a "better" more positive Vacuum Secondary actuation.
Put this is all just opinion, discussion, & bench racin', not at all intended as "gospel", or "the only way".
