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Thread: Mixture vs Jetting Question.

  1. #1

    Default Mixture vs Jetting Question.

    My truck is running pretty well right now, however, I have a few questions. I know my carb needs larger jets. Question 1: Will I be able to get my mixture correct if the jets in it are too small? Question 2: I used a vacuum gauge to set my mixture as directed by Holley. When I got to my highest vacuum setting the truck acts lean when I drive, but idles great. Again, I know my jets are to small. So if the highest vacuum reading is the correct setting (screws out about 3/4 turn) is it just acting lean because my jets are too small?

  2. #2
    Join Date
    Nov 2014
    Location
    Ont. Canada
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    1,396

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    Just off idle & light cruise, it's running off the idle ports & transfer slots. And then at some point the main boosters will start to flow. If jetting it up helps the lean spot, then you're good to go. If it doesn't and the only way to fix it is to enrich the idle screws, then that's what you have to do. Unless you want to get into drilling out the idle restrictor and enrich the transfer slots.

  3. #3

    Default

    Thanks for the reply. I made good progress and have the truck running pretty well now. I'm onto the rear jets now.

  4. #4

    Default

    Now that I have the truck jetted correctly, do I need to go back and check the mixture again? I can't find any information on it. Logic would say that the idle circuit wouldn't be changed with main and secondary jets, but I'm not a pro, so I thought I would ask.

  5. #5
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,396

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    The idle circuit should not change with a jet change. The idle circuit has its own idle restrictor & air bleed.

  6. #6

    Default

    Thanks for the reply man. I got it running great. I'm really pleased. I've done so much tuning/adjustment on this carb, I feel like I invented it.

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