Removing the idle down channel restrictions

[Cadman-iac]

 I was curious to know how others were removing the restrictions without damage to either the body or the restriction.
 I've been using Cliff's method of using a screw and pliers to pull them out, but it doesn't work all the time. If the restriction is too tight in the body this only cuts the lip on the restriction without pulling it out.
 On some of my damaged carbs, (ones I bought that were previously damaged and only good for parts), I began to use a drill bit to slightly enlarge the opening to make sure the piece has as little resistance as possible. This works good, but I don't want to try it on a good carburetor body without knowing if enlarging the top of the passage on the down channel will affect the flow/calibration. 
 With the damaged cores I tried this on, I placed a gasket over it to check if it still covered the passage, and it does, so the only thing I can see that might be affected is the flow.

 The reason why I was doing this is to get the restrictors out to use in calibration of other carbs. You can always open up a restriction, but to make one smaller it's not so easy. Even driving in a plug to drill out to the size you want you have to get the original one out of the passage first.

  On one junk core instead of drilling the top of the down channel to remove the restrictors, I drilled through the restrictor using a bit the same size as the passage and went all the way through the bottom to see exactly where the passage would have come out if the factory had gone further instead of intersecting at an angle just above the bottom of the bowl body.  Then I tapped the hole with a 6-32 tap and installed a really short set screw to plug the new hole.
 The purpose being that if you are trying different diameter restrictors in your carburetor, this would allow you to remove the set screws (plugs) and run a rod up through the passage to pop the restrictors out without causing damage to them and then you can easily install a different set and reinstall the plugs on the bottom.
 This works great on the junk core, but I have yet to try it on a good carburetor. I don't know if this will change the flow characteristics through the bottom of the down channels or not.
  Any thoughts?

 Rick

[Kenth]

After removing the original restrictor you may thread the hole with a 6-32 tap and installed a short brass set screw and drill the size you need.

HTH

[Cadman-iac]

 That's great to know, I wasn't sure how you shrink the orifice size.
 I just bought a few steel 6-32 set screws, but wasn't aware that you could get brass ones, that would make things much easier.

 Since I stripped a bunch of damaged carbs for parts I was able to gather a small collection of down channel restrictors to tune with, but it's still going to be difficult to swap them out each time. Having a removable drilled plug is a much better solution.
 Thanks for your input, much appreciated,

 Rick

[77cruiser]

https://www.mcmaster.com/
They have what you need too.
I like to thread mine, made some thread in idle tubes, moved the IAB to the top & threaded so I could change idle calibration without disassembly.

[Cadman-iac]

https://www.mcmaster.com/
They have what you need too.
I like to thread mine, made some thread in idle tubes, moved the IAB to the top & threaded so I could change idle calibration without disassembly.

 Those are some good ideas, I like that. How did you make the idle tube screw in, use a set screw and drill out the center to fit the tube replacing the collar normally used?  And does that leave enough of the hex socket so you can use an Allen wrench to install and remove them?
 I would imagine that you would have to have a mini drill press to do this with as well, right? What bits did you use?
 How were you able to relocate your upper idle air bleed, and where exactly did it end up, do you have any pictures?
 Very cool ideas,  thanks.

 The carburetor I'm currently working on has slightly worn idle tube locations so I can usually use a pick or a round jewelers file inserted into the top of the tubes to lift them out to replace with another set, and since the restriction is on the bottom this method doesn't hurt the tubes.

 As for using a drilled set screw for the down channel restriction, the factory set them down the passage a little bit.  Do you drill down a ways to recess your new restrictors or just leave them at the top of the channel?  Leaving them on top would require relocating the air bleeds I would think, as the set screws would cover up the existing ones, wouldn't they?

 I'm still working out in my head how all this stuff works internally and how it affects everything, so I'm sure to have some questions. I haven't been this deep into the inner workings of the Quadrajet before,  I've always just refreshed one with a kit and reinstalled it on the vehicle.
 This is the first one I've tried to actually tune for a specific engine using a different carburetor. I took a 454 carb and recalibrated it to use on a 350 using Cliff's book for reference and information from another site that someone named Lars had posted. I had found Lars information a few weeks ago but I've had Cliff's book for a few years. I mainly used the book for improving the E-Jet on an 81 El Camino.  But that one was a 350 carb on a 350, it didn't really need much recalibration.

 Rick

[77cruiser]

I use 10-32 x 1/4 in. long brass set screws. Have to shorten the tubes a bit drill the set screw & solder the tube in.
As for removing the restrictions a drill bit that is slightly bigger that the cup will grab it & sip it loose.

[Cadman-iac]

I use 10-32 x 1/4 in. long brass set screws. Have to shorten the tubes a bit drill the set screw & solder the tube in.
As for removing the restrictions a drill bit that is slightly bigger that the cup will grab it & sip it loose.

 That sounds like a good idea. How do you drill those out, on a small drill press,  or do you have another method?

[Kenth]

For the idle tube removal i use a small tube extractor.
I would not thread the holes for the idle tubes.

[mcx]

Kenth
Could you attach/link of this  “small tube extractor”…half the time I screw up the removal with Cliffs method.Thanks.
-Michael

[Cadman-iac]

I use 10-32 x 1/4 in. long brass set screws. Have to shorten the tubes a bit drill the set screw & solder the tube in.
As for removing the restrictions a drill bit that is slightly bigger that the cup will grab it & sip it loose.

 Just tried this, works great, thanks for the tip.

[Kenth]

Kenth
Could you attach/link of this  “small tube extractor”…half the time I screw up the removal with Cliffs method.Thanks.
-Michael

Michael
Finding the right size can be challenging, but mine have served me well in hundreds of Quadrajets. This allows you to reuse the original style of idle tubes without unnecessary work.
-Kenth

[mcx]

Thanks Kenth…I’ll start looking for one of those.