Cliff's Quadrajet Parts and Rebuild Kits
General Category => Quadrajet Carb Talk and Tips => Topic started by: novadude on September 18, 2025, 05:31:44 AM
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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?
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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.
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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.
If you remember where, please share. Do you recall the conclusions?
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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.