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Discussion Starter · #1 ·
At a steady cruise around 2500-3000 I get a miss. I have my idle feed restrictors dialed in (slow acceleration without squirters and no stumble) . My jetting is right (if not a hair big). Would this rpm range be in the idle air bleeds or the high speed air bleeds?
Its a 4150 650 cfm, proform body, holley base converted to 4-corner idle. Runs great everywhere else, just the cruise thing.
Thanks
Tracy
 

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That rpm is both circuits depending on throttle position, but remember, air bleeds only adjust the "authority" of the circuit they apply to. In other words, think of a soda straw with a hole. You suck soda through, the bigger the hole, the more aerated (emulsified) the fuel is.

Its not a 1:1 kind of "add more air bleed to make it lean" if you add more bleed you change the whole metering curve from top to bottom

If you have tunable bleeds I would start with reducing the idle air bleeds by .004 or so (you can also stick a small .010 wire in them and tape the wire to the bowl for a road test)

If you were slightly lean, that may do it. But if your transition circuit is very lean, you may have to open up the IFRs even though you think you may be there

Another trick is raise the float level, that makes more of a difference than you would think at low/mid rpm because the idle, transition and boosters are all more sensitive because they dont have to pull as hard to get the fuel moving
 

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Discussion Starter · #3 ·
Thanks, Thats what I needed. Am i correct that the inner set (towards the vent tube) are the idle and the outer set are the high speed? Should I do it with all 4?
Tracy
 

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The outer are the idle bleeds, you can verify by blocking one with your finger at idle, it'll stumble.

They are the LARGER ones as well. Should be the 4 outer ones. Inner should be the high speed bleeds and be very small.

Reason being is the idle bleeds supply most of the air for the idle circuit (mixed with fuel of course on the fuel side of the air fuel screws) while the throttle plates are you are on the main jet, most of the air is coming down the carb barrels, the high speed bleeds are just there to "churn up" the fuel to better atomize for a simplified explanation

Thats why the idle ones are bigger


<font size=-1>[ This Message was edited by: My427stang on 5/4/06 4:02am ]</font>
 

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Discussion Starter · #5 ·
I have a handful of blank AB's and will try going down .004 on all 4 corners. As a note, the missing at midrange was worse, I went up 2 jets in my primaries and it reduced it to I guess for a lack of a better term, mild miss.
 

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You have the right idea, but I'd check your float level too. It could be a smidge low, that makes a huge difference at part-throttle

BTW, find an on-line calculator for area of a circle.

Diameter is whatever your bleed is now, calculate area, then reduce it .004 and recalculate, compare he differences in area, I bet that's 10% difference. May want to just try .002 and raise the float level a bit
 
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