Register now to get rid of these ads!

1978 Quadrajet idle mixture adjustment?

Discussion in 'The Hokey Ass Message Board' started by atomickustom, Apr 24, 2006.

  1. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,000


    The stock Quadrajet on my 1978 350 has no idle mixture adjustment screws! I didn't notice this until I'd already gone to the trouble of cleaning the carb, bolting it onto my new manifold, and adapting all my linkages, etc. It runs fine, but I'm sure I could smooth out the idle a bit more if I could rich it up just a teeny bit.
    There are just silver metal plates filling the round holes where the screws would normally be. Are these just covers? If I pry them off, will I destroy my carb, or will I find adjustment screws patiently waiting for me to adjust them?

    I DID try to search to see if this has already been covered. If it has, please just post a link to the old discussion.
    Also, I know that a 1978 Quadrajet isn't exactly "traditional" and don't need anyone to remind me. The entire running gear in my '53 Chevy is from a donor car (1978 Impala wagon = CHEAP), and I'll take "cheap" over "traditional" any day. You wouldn't believe how many parts you can use off of one good donor car!
    Joined: Feb 8, 2006
    Posts: 565


    There Are Just Covers I Ussally Jusy Drill A 1/8 In Hole From The Bottem Up Angle Toward The Front And Stop Before You Go Through All The Way And Drive Out The Cap With A Punch.

    Good Luck
    Joined: Nov 22, 2005
    Posts: 7,594

    from SIDNEY, NY

    25 years ago, all of the parts stores sold "modification kits" that came with a hole saw to cut out the plugs, and a special adjusting tool, since the ends of the mixture screws resemble a clutch head, like '40s and '50s Chevies are held together with. Thexton made such a kit, but I don't know if they still do.
  4. Flatman
    Joined: Dec 20, 2005
    Posts: 1,975


    You might be able to grab the screw head with some small needle nose pliers, once you get the covers off :D
    Those Q Jets were great carbs, huge secondaries:eek:

    Register now to get rid of these ads!

  5. 53sled
    Joined: Jul 5, 2005
    Posts: 5,821

    from KCMO

    Lisle tool and maybe Motormite sell q-jet tools with the funky end. Drill a small hole, run a screw in, pop out.
  6. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,000


    Thanks for the info, everyone. I'll be drilling and popping soon.
  7. bigdog
    Joined: Oct 30, 2002
    Posts: 399


    Those mixture screw plugs might be hardened steel- they were on the one I just did. Drill bit won't touch 'em if they are. I went and dug out the instructions for removing the plugs.

    1.invert throttle body
    2. place punch between two location marks over idle mixture plug
    3. break out throttle body to provide access to the hardened steel plug, drive plug out

    4.late models-cut 2 parallel slots on either side of the location marks using a hacksaw. slots should not exrend beyond 1/8 inch past the marks
    5. position a flat punch at a 45 degree angle between the ends of the saw marks in the throttle body, drive the punch between the slots causing the slug to break off.
    6. hold a center punch in a vertical position and drive it into the steel plug, then angle the punch 45 degrees and drive the plug out.

    Fun, huh? always loved beating on carburetor with hammers.

Share This Page

Register now to get rid of these ads!


Copyright © 1995-2013 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.