Disconnecting secondaries

Short answer is no. I assume you have a Quadrajet on there. You can always adjust the secondary air valve a little tighter if you think the're opening too much/early.
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Be very careful with this adjustment. Tiny weak spring and 1/8th of a turn makes quite a bit of difference.

If you decide to do a complete adjust from scratch.......P.S This is done with the engine off.

Loosen the set screw with a screwdriver in the adjuster so it wont snap back on you.
Then slowly turn the adj counterclockwise while pushing open the air door.
Once it will stay open on it's own, slowly go clockwise until the tention will just shut the door.
From there, go about 3/4 of a turn and lock the set screw. "Caution" don't go more then 1 full turn from the start.
At this point you can road test and see how it feels, and make small adjustments as needed.
One tip....If the door opens just free reving the engine, the adj is a little too loose for what your trying to accomplish.