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I have built and ran small i.c. carburetors originally designed by George Britnell and by Malcolm Stride. Both of these carburetors included "air bleed" screws in their design. Recently, I seen a post by George Britnell saying that he no longer used the bleed screws in his carburetor design. I myself have found that they don't seem to have much effect on how well an engine runs. They give a very small bit of influence on how the engine idles, but I question whether or not any improvement they may add will offset the bother of using them at all. I am soliciting opinions from other knowledgeable folks out there who have built and ran these small carburetors with "air bleed adjustment screws" on them.---Brian rupnow
This is my own opinion but I think the air bleeds we use don't make sense to me. When using the carb off idle the air bleed is blocked, makes sense. At the idle position the air bleed is exposed to the top of the barrel hole and bleeds air through the barrel the same as if it were off idle sucking fuel with it. I believe the air bleed should short circuit the barrel and feed air straight to the bottom of the carb so no fuel is brought in with the air. Then I believe there will be a leaner mixture and a more noticeable difference in how they respond to the bleed. If the bleed air is fed into the top of the barrel the mixture won't change. I plan to modify the V8 carb to test my theory but time has not permitted.