Ok, been poking around the web trying to find an adjustment procedure for secondary idle screw adjustment. I would assume this would be done in conjunction with the primary idle screw adjustment. I just guessed on how to do it last night when I started to tune my new carb.

FYI I am not talking mixture adjustment screws...I am talking secondary blade adjustments.

what is it that you are trying to do? is it idling to high?

I am attempting to set the idle properly. This carb has secondary idle adjustment. I would assume that both primary and secondary blades should be set equally open but I do not know how to do that. I just eyeballs it last night.

Was it purchased new or did you rebuild it? Generally you turn the one idle screw. On the throttle lever where the idle screw is there is a cam that turns the secondary lever.
The secondary does not open the exact same time as the primaries there is a slot in the throttle lever when the arm is pulled to the end is when the secondary throttle blades open

The carb is new. It has primary AND secondary adjustments for idle...I'm not talking mixture screws either. I am familiar with the linkage.

I usually give front and back 1/8 turn at a time till she idles right. If you go to far on the front blades and start getting fuel dripping from the boosters back the front blades out and try to get it to idle off the rear. It seems like the front booster like to drop fuel quicker than the back. It's ok to have the rear blades open more than the front or vise versa. When your messing with the adjustments after you make an adjustment crack the throttle a couple times and clean it out then let it come back down to an idle to see what you have...

I set the primary side throttle blades so the transition slots are within spec. Secondary side, I close the blades completely, then give them 1/2 turn to just crack them. Fire the engine, if you need to raise or lower the idle speed, use the secondary screw..

Another thing Ive found, with tuning the idle mixture screws on a 4 corner idle carb. I've had complaints where guys couldnt get the lean sneeze out of their carbs when planing off. At low RPM, the signal is still very weak at the boosters, and it can still be relying on the primary idle circuit, to help fuel the engine while planing. While I know the instructions say to back each mixture screw out evenly all around, I've found having the primary sides out more than the secondary sides, helps with the lean sneeze. For example, if the best idle is with all 4 screws out 1 turn, try 1.5 turns in front, .5 in the back, or along those lines. For the most part, secondary idle circuits on holleys, are there so that in rarely driven hard classic cars, dont get stale fuel in the secondary bowl, or if you have some ridiculous cam in the engine.

Huh! Never thought of doing that with the mixture screws but makes perfect sense.

Almost all Holley's have secondary throttle blade opening adjustment screws...it's just you have to take carb off and turn upside down to get to them. Pain in the nuts if you have to access them. A few come with normal screw as found on primaries.

Quick Fuel, and a few others, are just cool by giving you a normal type screw set up for them.

I added them to my carbs. They are neat.