Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

help with figuring out my idle issues.

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bruno:
I have a post going in the “tips” section that covers all the details( help with 17082224). if I should stay in that post, let me know.

I have a specific question about the LIABs. I have been trying to shrink them down to 063. I thought i got them close, but maybe not. i tried the check ball method, and didn’t have much luck. i ended up using a sharp punch around the perimeter to peen it over, but it doesn’t leave a round hole anymore of course. so measuring is harder. I do have pin gauges, but only up to 060. turns out I don’t have control with the mixture screw on that side either.  I have been told to install a brass set screw and drill it. I would like confirmation this is an “acceptable” fix? I’m leery to drill a 8-32 hole cause it will ruin the carb if it doesn’t work. I assume if this is okay, that th set screw needs to be ground so it doesn’t block the passag or throttle bores at all?

I also inadvertently drilled the down channel restrictions to .060”( caliper zero error) will this work, or provide too much fuel? my idle tubes i’m pretty sure are .038” idle mixture screw holes are .090” springs not binding.( measured depth with and without springs)

68 chevelle, 396 325 hp stock minus “RV” cam, unknown specs, but “small”
timing is currently 10 initial, 26 more centrifugal, starting at 900-950 and all in around 35/3600. VA adds another 14. idle vac is 17.5

fighting a bog when cracking open the throttle from idle.

if all else fails, i have a 17084226 i can rebuild as well.

bruno:
something i should add is I’m still running points. I don’t remember the specs at the moment, but i did set them up with a dwell meter. I’m not sure if bad points would cause my bog as the i’ll is smooth, and even at 3500 it seems smooth. it’s just the quick whack of the throttle that’s giving me issue. accel pump is from cliff, and has a good shot of fuel. tried both settings.

77cruiser:
I used 6-32 brass set screws.

bruno:

--- Quote from: 77cruiser on March 12, 2026, 10:17:37 AM ---I used 6-32 brass set screws.

--- End quote ---

I have some 8-32 brass ones that should be here today. did the 6-32 work with an allen key after drilling? or did you install them and then drill them? I assumed a .063 hole would cut into the hex on a 6-32.

77cruiser:
The hex is 1/16 or .0625.

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