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Secondary main well air bleed tubes

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novadude:
Let's talk about secondary air bleeds.  I've noticed that most Chevy carbs are 0.026-0.028".  Cliff's book recommends drilling all to 0.036", and I believe many BOP carbs came with .033-.036" tubes.

What is the effect of increasing the air bleed size?  I am thinking that this might make the secondaries richer on initial opening - bigger bubbles lead to better initial flow when fuel starts moving thru the nozzle.  I am also thinking that larger bleeds may trend a little leaner at higher flow due to more air mixed with the fuel.  Basically, the slope of fuel curve relative to air flow would change.  Am I correct in my thinking?

How much impact does the secondary air bleed have?  Has anyone done back-to-back tests changing nothing but the air bleed size?

77cruiser:
Somebody did do a test on this but I can't remember where. Might have been Class Racer, but just not sure. I don't think it was here.

novadude:

--- Quote from: 77cruiser on September 18, 2025, 10:49:47 AM ---Somebody did do a test on this but I can't remember where. Might have been Class Racer, but just not sure. I don't think it was here.

--- End quote ---

If you remember where, please share.  Do you recall the conclusions?

77cruiser:
If I remember right a couple HP up to .043. Might have been on the other carb forum that kinda died out. Seems like I asked Tuner & I got salt to taste, so I take it whatever works.

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