Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
How Much Idle Bypass Air?
von:
Chevy 454 with 9.0-1 CR and cam with a fair amount of overlap. 10" vacuum at idle. Using a '68 Q jet #7028210 that had no idle bypass air, rebuilt to recipe #2 specs. Drilled holes in the primary throttle blades for idle bypass air. What size holes would be correct? Started with .088 but doesn't seem to be enough.
Cliff Ruggles:
You will also need to add idle fuel by enlarging the idle tubes and idle down channel restrictions. Adding bypass air alone will most likely not be enough for that low of a vacuum reading at idle.....Cliff
77cruiser:
I ended up @ .140 on my 385 that has about 11" vac. but it whistles a bit @ idle.
von:
Yes as I stated I rebuilt to recipe #2 specs. I added idle fuel by enlarging idle tubes to .038 and idle down channel restrictions .055. Idle mixture screw openings are .093.
von:
Also, would idle bypass air openings in the throttle plates be the same size as openings in the base plate as far as effectiveness? In other words, to equal .135 of factory idle air bypass in the carb body, would .135 holes be drilled in the throttle plates?
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