Author Topic: Main Well Bleed Tube Depth  (Read 898 times)

Offline Brian B.

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Main Well Bleed Tube Depth
« on: December 02, 2021, 12:03:36 PM »
Hello.  Could someone please advise to what length should the Main Well Bleed Tubes extend beneath the air horn on a 1974 Quadrajet 7044270 and how critical is it for them to be at that exact measurement? Thank you.

Offline Brian B.

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Re: Main Well Bleed Tube Depth
« Reply #1 on: December 04, 2021, 12:08:30 PM »
FWIW.....I set mine at one inch today and car performed fine.

Offline Cliff Ruggles

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Re: Main Well Bleed Tube Depth
« Reply #2 on: December 05, 2021, 02:33:29 AM »
From the factory they are driven in until the ends just barely stick above the material in the airhorn that holds them in place.  It's really not a big deal and they will work fine if you drive them in a little further.  It's one of the parts of the carburetor where exact precision really isn't required, at least from the testing I've done in that area.  I'd also note here that the Ford 429 Cobra Jet carbs didn't use them at all.

Prior to writing my book I did extensive track and dyno testing and part of it included bleed tubes.  I found that using a .036" bleed tube was a very good place to be with long tip secondary rods in the .040-.052" range.  In really hot/humid weather at my altitude (about 1200' above sea level) I could got a tad leaner but started to experience some "surging" past .060" but no detonation or other negative symptoms.

Others may get completely different results.  This often happens when you aren't using custom machined secondary rods all cut from the same cores with the same tip length, upper section size/taper and same included angle leading to the tips....FWIW........Cliff