(Long background story here). I finally figured out where the idle bypass air passages run, and it surprised me that I haven't seen any info about this online, because rather than drilling holes in your throttle discs, I think you could edd or enlarge these bypass passages a lot easier, even in a 750-cfm Q-jet. If I'm wrong about this, please correct me, this is just what I've found out aboutmy two Q-jets (a 750-cfm #7044244, and an 800-cfm #7042240) Here are pics of the idle fixed air bypass passages, from the top of the carb to the bottom. It's a long, strange trip...
Here's the airhorn with its gasket, the blue arrows indicate the passage inlets, the red arrows indicate where the passage goes through the gasket headed for the carb main body.
Here's the carb main body with the same airhorn gasket in place. Blue arrows indicate the air passages through the gasket, red arrows indicate holes into the same area, but don't seem to have any purpose that I can see.
Here's the main body without the gasket. The air passages are simply big voids in the body casting, with holes drilled through to the underside (blue arrows).
Here's where my story gets wierd, the arrows indicate where the air passages *should* be, but as you can see mine aren't drilled. o No: Yes, this is an 800-cfm Q-jet - :Smarty: I dug through my receipts, it's an AC Delco remann'ed unit I got from a dealership that was shutting down years ago. Still have the nice Delco box and tray...
Here's the underside of the throttle plate / baseplate, with everything I need for idle bypass passages except a couple of holes. Copperheadgs1 says his is .0890 or a #43 drill bit, anybody got anything different please chime in.
Interestingly, both my 750- and my 800-cfm Q-jets are exactly alike on this, so I'm thinking that you could add an air bypass to your 'little' Q-jet and use it on either a hot 350 or a 455 if you wanted to...