Question on Holley 4150 4-corner idle system

[cudabob496]

On my 850 DP, if the idle adjust screws at each corner are open too far, so that it is making a rich idle
situation, will that affect richness up through the rpm range, or will the affect disappear once, say,
you get above 2000 rpm?

I told a Holley tech I had each screw open 1 and 1/2 turns, and he said it would be too rich, but
I did not ask him the above question.

[Oldschool]

Why 1 and 1/2 turns out? That will usually be too rich. I run mine about 1/2 - 3/4 out and adjust the fast idle up just a hair to expose a little more of the transfer slot. My car is running two 750 HP's on a cross ram and it idles great and has crisp throttle response off idle. 1 and 1/2 turns is just a baseline to get it running and then tune from there...   

[Chryco Psycho]

When I do initial engine break in runs I often cheat the jetting with the idle mix screws , once I get it to 2000 rpm I tweak the idle mix screws which often smooths out the engine , so if I have to turn out the idle mix the jetting must be small or the reverse .

[cudabob496]

ok, thanks. 1 and 1/2 turns is the Holley recommended starting point for the screws, before
you start adjusting them based on vacuum readings. I'll have to play with them some more!

[Chryco Psycho]

If you have low vacuum & have the idle speed turned up a fair amount it will help to drill a small hole in the throttle plates to increase airflow while keeping the plates closed down so the isle mix can be adjusted properly

[cudabob496]

Weird, I took all 4 idle screws to 3/4 open, would not idle. Just quit.
Took all 4 to 1 turn open, would not idle, quit.
Took all 4 to 1 and 1/4 open. Idles great, and on the road
my AFR went from around 11 to around 12.8, on up to about 3000 rpm.
whodda thunk some idle screws could be contributing to my overall AFR
up to about 3000 rpm.  AFR drops after 3000 rpm, due to secondaries opening
I assume.

Man, these AFR meters are a real help, if you want to know whats going on in
your carb/combustion chambers.

[Strawdawg]

or the power valve circuit