Question about single main bleed Quadrajets...

[firefox3]

Mr. Ruggles, why are the later model Quadrajets, using single main air bleeds, more difficult to tune?

Thank you...

[Cliff Ruggles]

They aren't really any more difficult, just use slightly different parts.  The primary metering rods have larger .036" tips, and "step" down instead of full taper between steps. 

Using only one main airbleed, which is "indirect", puts more pull to the jets.  This changes the entire fuel curve, putting more signal to the jets with less emulsion air. 

They are very good carburetors.....Cliff