I've set up my Q jet ( '73 Chevy 350, 7043202) exactly per the 2nd recipe specs. I even plugged the large .120 main air bleeds and redrilled to .070. The carb is on a Chevy 396 with mild (221/233 @.050) perf cam and stock intake, 12.5 to 13" of vacuum at idle in neutral. The dist is recurved and has 14 deg initial advance with additional 12 deg vacuum advance on full manifold vacuum. The carb specs are as follows: both sets of main air bleeds .070, mixture screw holes .098, idle bypass air .109, idle tubes .038, idle channels .055, upper idle air bleeds .070, lower idle air bleeds .070, primary jets 73, primary rods 44B. Primary rods stay down at idle. I've verified idle bypass air is open and working.
Problem is no control with idle mixture screws. No appreciable difference in idle speed or vacuum from seated to 4 turns out. The pass side one will slow the idle down a hair and 1/2" of vacuum if seated. If I pull a small manifold vacuum line off the idle the idle speed increases a lot. The only thing left I can think of is to drill holes in the primary throttle plates. Anything else I should try first?
