Curb Idle Screw Settings on 426 Hemi

[Shadetree]

Hello, I have a set of original 1970 Carter AFB Carburetors on a 1970 Modestly Built 426 Hemi (Dyno-590 HP at 6,200). The car idles decent but I’m always up for learning and any improvement. I have set the idle mixture screws on the rear carb to most vacuums and then richened another 1/2 turn. The curb idle screws are currently set to where both carbs are playing an equal role. Example-if you turn either curb idle screw any whatsoever the RPM’s increase. The lead that covers the idle mixture screws on the front carb hasn’t been removed. My questions are should I remove the lead so I can tune those idle mixture screws also or should I leave them alone? If the lead needs to be removed, what is the best way to do so? Should I engage the curb idle screw on both carbs to the point where the car is idling off of both carbs equally (that’s the way it’s set currently) or is the rear carb supposed to assume more of that responsibility?

 

[Budnicks]

I would say the factory 'built engine', the rear carb was intended to do the idle mainly
probably why the other screw was leaded off, so you couldn't mess with it
front carb was set at the optimum place to cover/uncover the idle circuit,
butterfly setting

if you're actually making 590hp @ 6,200 rpm
your engine is nowhere near stock anymore, has different 'tune needs'
tune it to what the engine needs & wants now....

 

[Shadetree]

I would say the factory 'built engine', the rear carb was intended to do the idle mainly
probably why the other screw was leaded off, so you couldn't mess with it
front carb was set at the optimum place to cover/uncover the idle circuit,
butterfly setting

if you're actually making 590hp @ 6,200 rpm
your engine is nowhere near stock anymore, has different 'tune needs'
tune it to what the engine needs & wants now....

There’s the Dyno sheet. I’m not sure either, that’s what I need to know from someone that has first hand experience, if it’s worth uncovering the idle mixture screws on the front carb and should they be supplying fuel equally at idle.

 

[Geoff 2]

You only need two adjustable idle mixture screws to provide idle fuel. That is why Ch designed the system that way. I presume the front idle screws are supplying some idle fuel, with the rear screws used for 'fine tuning'. Adjust screws for highest idle rpm.