Can someone explain to me how i can be certain that im runnin on the idle circuit when adjusting mixture screws?

I fear that this whole time ive been trying to tune my main circuit because my rpms are idling at 1200-1500 rpm. I tried lowering the rpms with the idle speed screw but the car just seems to start shaking and gives me a hard time.

Am i going about this the right way? Not 100% on how the idle and main circuits work. Does one engage at a certain rpm?

Any help appreciated

 

What kind of carb, and what kind of engine and cam?

 

Holley 4160, 305 Engine. Cam isnt stock but it seems like a baby cam, not really that audible.

Dont know the engine build specs.

 

Start with the steps in the Holley tuning sticky in the top section of this forum. When you set the throttle plates using the stated method, there won't be any doubt that you're running on the idle circuits.

 

whats the list number on your carb? if it is a 6610 then your idle circuits will be opposite of a regular 4160. meaning turning them in will be richer and turning out will be leaner.