Center carb 340-6

Michael Siple said
going to try that simple check with the bleed holes - if it is set correctly it won't increase or decrease ? Think end carbs still have the plugs

If I couldn't have adjusted the outboard carbs, my 440 would never have run properly. When I had my running Holley carbs modded by Promax, to accommodate current motor mods and even more importantly, future significant mods, I had the angled idle mixture screws throttle plate installed in the rear carb.

Michael Siple said
if it is set correctly it won't increase or decrease ?

Correct. If it does change, for your own sake, remove the lead caps and gently, ever so slowly and MUCH more slightly turn the idle screws on the outboard carbs! They are WAY more sensitive to adjustment! I knew the outboard carbs were a problem when I bottomed out both idle mixture screws on the center carb metering block and the engine ran better.
The outboard carbs were contributing WAY too much fuel AND air. The air part was fixed by adjusting the rods that "hold them closed" and likewise slide out of the way in the slot of the center carb mechanism that allows them to open.