Recent Posts

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21
Quadrajet Carb Talk and Tips / Re: What are these holes for?
« Last post by 77cruiser on November 07, 2025, 10:40:55 AM »
No idea.  Someone on the other carb forum (when it was still active) bought a quantity of taps in that size and sold me one for a good price.  They are pretty expensive to buy just one.  I see Allstate sells them in a kit with a tap, but they are not cheap.

https://www.mcmaster.com/products/taps/taps-1~~/thread-size~10-40/chamfer-type~plug/chamfer-type~taper/
22
Quadrajet Carb Talk and Tips / Re: What are these holes for?
« Last post by 77cruiser on November 07, 2025, 10:35:10 AM »
I measured them & I used 1/4 inch for the tubes.
23
Quadrajet Carb Talk and Tips / Re: What are these holes for?
« Last post by Cadman-iac on November 07, 2025, 10:06:33 AM »
OK I see I put 1/2 inch should have been 1/4 inch. I'll measure later to make sure.

 Well I can tell you that the 1/8" long ones are definitely too short for this.  A 1/4" long one would probably be perfect.
 I made a couple last night but wasn't happy with them, I'm afraid that the tubes will come out if subjected to too much heat or vibration, even though they're soldered in.

 Novadude,
 Thanks for the explanation/clarification on the idle circuit.  I appreciate it.

 Rick
24
Quadrajet Carb Talk and Tips / Re: Secondary POE restrictions
« Last post by Cadman-iac on November 07, 2025, 10:01:28 AM »
The secondary POE restrictions are located in the air horn at the front edge of the air valves.
Most are above the edge, some at the edge and a few under the edge.

 So what Cliff is calling the POE restriction is what is also referred to as the secondary accelerator nozzles?
 Just a matter of terminology causing the confusion. Thanks for the explanation Kenth.

 Rick
25
Quadrajet Carb Talk and Tips / Re: What are these holes for?
« Last post by novadude on November 07, 2025, 07:31:01 AM »
No idea.  Someone on the other carb forum (when it was still active) bought a quantity of taps in that size and sold me one for a good price.  They are pretty expensive to buy just one.  I see Allstate sells them in a kit with a tap, but they are not cheap.
26
Quadrajet Carb Talk and Tips / Re: What are these holes for?
« Last post by 77cruiser on November 07, 2025, 06:59:23 AM »
I've seen them too, after I had done mine. Wonder why that thread, so they could sell a tap too?
27
Quadrajet Carb Talk and Tips / Re: What are these holes for?
« Last post by novadude on November 07, 2025, 06:38:49 AM »
Allstate carburetor sells pre-made threaded tubes, but tap size is weird (uncommon).  I've used these before.

https://allcarbs.com/product/rochester-quadrajet-idle-tubes-threaded/?v=0b3b97fa6688

28
Quadrajet Carb Talk and Tips / Re: What are these holes for?
« Last post by 77cruiser on November 07, 2025, 06:19:21 AM »
I used the 10-32 to make idle tubes, you need some extra tubes. If you have a couple of junk cores to pull the tubes out of you're set. I can't remember off hand the length of the screws 1/2 in. I think & the tube have to be shortened the depth of the hex in the screw.

OK I see I put 1/2 inch should have been 1/4 inch. I'll measure later to make sure.
29
Quadrajet Carb Talk and Tips / Re: What are these holes for?
« Last post by novadude on November 07, 2025, 05:33:41 AM »
On this subject Novadude, if you increase the UIAB's this will lean out your idle mixture, if im understanding it correctly.

Yes.  I believe that is true.

 
Quote
By increasing the LIAB's then this will fatten up, "enrich" the off-idle mixture, again if I'm understanding it correctly.

I'm not sure about this one.  I think larger LIABs will actually lean it out until the throttle blades get past the LIAB.  By this point, the main system will already be active.  In my experience, the larger 0.078" LIAB carbs never seemed to run as well off-idle as the ~0.062 LIAB carbs. 

Quote
Enlarging the idle tubes enriches the whole range of the idle circuit, correct?
 

I think this is true

 
Quote
And by increasing the IDCR's, this would have the same effect as increasing the idle tubes, but also increases the effective range of the idle circuit, is that correct?
 If not, what am I missing here?

Larger IDCR will increase the amount of mixture getting to the transfer slot and idle screws.  If the UIAB is too large, or idle tube is too small, it could still end up lean off idle.  At least I think that is how it works.

   
Quote
And increasing the idle by-pass air it allows you to close the throttle plate more to prevent any nozzle drip, in addition to being able to increase the idle speed without changing the throttle position, I think, right?[/quote']

Agree

 I was up late last night reading Doug Roe's books trying to get it straight in my mind.

  Another question, going through what I need for various sized drilled set screws I couldn't remember where the 10-32 screws were used, or did I order those by mistake? Do you use this size for anything?

 Kenth, Novadude, thanks for all the help and patience on this. Im beginning to think that I don't understand everything I know about this carburetor, lol!
30
Quadrajet Carb Talk and Tips / Re: Secondary POE restrictions
« Last post by Kenth on November 07, 2025, 05:25:29 AM »
The secondary POE restrictions are located in the air horn at the front edge of the air valves.
Most are above the edge, some at the edge and a few under the edge.
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