Obviously iiwii....... and if it’s working good that’s really all that matters........ but it seems really odd to me that adding 003” to a .066 hole(+.0003197sq/in)in an idle air bleed would change the idle speed by 300rpm.

ok, I just ran some numbers. going from .022" to .033" increased the area 225%, that's a lot. so going from .066" to .069" is about 9.5%. so maybe a 9.5% correction isn't bad at the IAB. i'd still look at stuff like leaky power valve (fluttering), float level/fuel pressure vs small needle and seats. i'm done; good luck!

ok, I thought I was done. the 225% is high (I think). the .022" jet is 44% of the .033" jet, so maybe about 150% change. still a lot and further than I have gone.

The .033" is really a shot in the dark. But you know once I think about it, did I just only change how much the mixture screws are screwed out ? I started at .022/.066 with screws at 2 turns out. Now at .033/.069 at 1.25 turns out ? Surely there's more to it than that, can't be that simple..........

You’re right..... it’s not that simple.

The air bleed/ifr relationship determines the A/F ratio mix of the circuit.

The mixture screws adjust the volume of that mix to the discharge ports.

If you say so.

Does it idle in gear better than before?

If so...... then it’s not really the same...... is it?

so if no fuel goes thru the secondary slots, and I can see were there may not be much with slot not being on the suction side of the throttle blades, then what does the slot do? my thoughts were; if there's an idle bleed boss on top of the body it can be drilled, and the body had a passage down to the base plate, then why couldn't it all get connected. . tricky part will be the base plate. of course without something in hand to look at I know i'm making some assumptions. IIRC the metering plate was similar to a 6pak and I know back in the day I understood the idle feed restriction, but i'm sure I didn't understand the relationship between all the parts and passages. anyhow, it's all a thought.

I know from playing with a factory 440hp avs with no secondary idle circuit and switching to an edelbrock 1407 that does have a secondary idle circuit there's almost night and day difference in low rpm engine burn and vaccum. I never thought a lot about how dramatic the difference was until this discussion. I know from playing with 6paks the primary carb circuit is really screwed up and needs mods. none of us do the mods so we just compensate for the problem by going after the secondary idle circuit which I think makes the engine burn dirty. I know the 1407 burns a lot cleaner than the avs. circumventing ma-mopars smog crap can be a brain teaser.

That’s what I was saying earlier.
If the carb being used here doesn’t have the constant idle discharge ports...... I’d be adding them, along with whatever mods to the main body were necessary to facilitate the proper function of one of the aftermarket metering plates that can utilize std jets(like a QFT 34-2).