Do any jets from other carbs fit Thermoquads ?

Fuel and Air Systems

  1. 4bblfreak

    4bblfreak Well-Known Member

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    question- is there any interchange-ability between other makes/models of carburetor jets, and the jets in a Thermoquad ? I didn't spec it out yet myself, but does anyone already know what the thread size is on the 72-up TQ jets ? I have read on the net today using Holley jets in a TQ. I compared the 2 and Holley jets don't just thread right in, they'd have to be forced in, because the thread size on the Holley jets appears to be a tad finer pitch.
    #2, the new Holley Demon Thermoquad knock-off carb, has interchangeable parts with the old TQ, namely the needle valves, floats, and accelerator pump shaft. Do the jets also interchange ?
    any help appreciated, thanks.
     
  2. GTX JOHN

    GTX JOHN FABO Gold Member FABO Gold Member

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    If you put in primary Holley jets = Better get the right size the first time as
    you will bugger up the threads (20 vs 24) in the phenolic.
    I also think the perhaps the metering rod will not function right with the different
    Holley jets because of different height.
    I do have a large asst. of Thermoquad jets and a fixture to drill them that a mainly
    used on the secondaries as they are unique.
     
  3. rumblefish360

    rumblefish360 I have escaped the evil Empire State! FABO Gold Member

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    In short, “no.”

    IF! The bowl under the jet becomes unglued on both sides, you can tap the thread size and pitch in and re blue the bottoms back on. This I have not done—- yet…

    As John has noted the height is of concern on the jets. Adjusting the tree height should do it. “should”

     
  4. 4bblfreak

    4bblfreak Well-Known Member

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  5. 4bblfreak

    4bblfreak Well-Known Member

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    GTX John the NHRA SS class racer, said he taps his for Holley on both primary and secondary, carefully, in an older thread elsewhere on the net...you can tap coarse to fine using a bottom tap i.e. not as much lead taper in the tap, and perhaps let the small bowls under the jets in place... but...how long will it hold. my experience with rigging like that is...after a few jet changes it'll be stripped out altogether. the threads definitely will be compromised to some degree. there is a brass insert in the bowl with the threads in it, so it's not threading into the black plastic itself. my gut told me years ago, these carbs are cheap enough used in junkyards, scrap piles, sway meets, just buy a number of emission carbs post-'77 model years, and drill those jets in increments beyond the stock size. the jet/spring kits are still on Ebay $50 free shipping for 8 pairs of jet sizes and power piston, accelerator pump springs, which is a deal. thanks for the replies fellas...
     
    Last edited: Jun 24, 2022 at 6:39 AM
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