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91
Dialing in your rebuilt Quadrajet carburetor / Re: help with figuring out my idle issues.
« Last post by novadude on March 13, 2026, 12:33:27 PM »
Jim... what do you do to make sure the setscrews don't come loose?  Having anything threaded like that in the throttle bore makes me nervous.  Is 1/8" long short enough to not protrude into the idle down channel and restrict flow to transfer slot and idle needles?
92
Dialing in your rebuilt Quadrajet carburetor / Re: help with figuring out my idle issues.
« Last post by bruno on March 12, 2026, 03:19:56 PM »
Quote from: 77cruiser on March 12, 2026, 03:16:54 PM
The hex is 1/16 or .0625.
ahh. perfect. thank you very much.
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Dialing in your rebuilt Quadrajet carburetor / Re: help with figuring out my idle issues.
« Last post by 77cruiser on March 12, 2026, 03:16:54 PM »
The hex is 1/16 or .0625.
94
Buy Quadrajet Parts, Quadrajet Kits, Service / Re: Buying Parts and Rebuild Kits
« Last post by ourkid2000 on March 12, 2026, 03:07:15 PM »
Hey Cliff, I wanted to buy primary jets for my carb but I wanted to go up one size. How can I order this off your website because if I put the carb # in, I'll get a 71 and I'd like 72's instead.
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Dialing in your rebuilt Quadrajet carburetor / Re: help with figuring out my idle issues.
« Last post by bruno on March 12, 2026, 01:43:30 PM »
Quote from: 77cruiser on March 12, 2026, 10:17:37 AM
I used 6-32 brass set screws.

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.
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Dialing in your rebuilt Quadrajet carburetor / Re: help with figuring out my idle issues.
« Last post by 77cruiser on March 12, 2026, 10:17:37 AM »
I used 6-32 brass set screws.
97
Diagnose a Quadrajet carburetor problem / Re: Quadrajet Throttle Body Swap - Will it work?
« Last post by Kenth on March 12, 2026, 05:55:29 AM »
I have managed to loosen of maybe 1 out of 10 APT screws in the throttle plates with the help of various sprays and heating with, among other things, a butane torch.
Nowadays I don't even bother trying.
If the carburetor needs jets or main air bleeds replaced, it will show up during the tip-in test.
98
Diagnose a Quadrajet carburetor problem / Re: marine quadrajet 17082515 on gm 4.3
« Last post by Zyen on March 12, 2026, 04:46:19 AM »
Quote from: Mudsport96 on March 07, 2026, 09:17:57 AM
So speeds are GPS verified that was one of my concerns.
right, i see a lot of posts that use the 'wish-o-meter' in the dash.  gps is the way to go.
Are all props from the same manufacturer?
no, they are not.  all are good condition ebay specials.  size and part# are factory stamped and visible on all.  no visible damage on 17, 19, 21.  23 has some slight edge scraping, but no bends or cracks.  21 appears new; no rub marks on inside splines when i got it.
I know outboard props of the same pitch and material can have different speeds from different cupping and rake. And something is way off with the 17p I would almost say it is damaged or marked wrong. Typically you get LESS slip with lower pitch.  15p@4600 is 35mph at 6% slip is why it think the prop is the problem there.
yeah, i agree...and it's a 4 blade, which makes it worse.  also, this prop acts funny, like it's not 'catching' water.  sluggish, hardly any 'pull'....and the 19p feels the same.  starting to wonder if the hub is slipping.  will have to look when i get time.

Okay back to the engine.
One thing I am curious about is the balancer. I myself, would pull the number one plug and use a piston stop to positively verify TDC lines up with the mark on the balancer. Over the years I have seen a disturbing number of balancer that were more than 4 degrees inaccurate. I am not saying that is definitely your issue. But, in the off season it doesn't hurt to check. PLUS, if it is wrong, you are possibly fighting two issues. Carb and timing ( that looks correct but is not.).
the balancer is new (came with engine) and i eyeballed it before i put the heads and intake on, using feel from btdc/atdc piston movement.  my thumb isn't exactly a positive stop, but it's damn close.
Another thing to try is if you have a buddy you trust to slowly block the carb and see if richening it up helps speed, richer secondary rods.
that's easier said than done...i have one i trust to help, and our schedules clash.  i'm working on teaching my oldest daughter (15) to pilot confidently enough that i can mess with engine at wot....but it's a slow process. 
Thats all I can think of, and I may be way off. I like to try to help, but online diag sucks, I prefer hands on.
for sure.  i appreciate the time and suggestions.
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Dialing in your rebuilt Quadrajet carburetor / Re: help with figuring out my idle issues.
« Last post by bruno on March 11, 2026, 07:42:19 PM »
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.
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Dialing in your rebuilt Quadrajet carburetor / help with figuring out my idle issues.
« Last post by bruno on March 11, 2026, 07:22:06 PM »
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.
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