Results 1 to 5 of 5

Thread: Install problem---High Idle

  1. #1

    Default Install problem---High Idle

    Hi Guys,
    I have recently installed a new Holley Truck Avenger 670 on my GMC. I was replacing an old Quadrajet with lots of missing parts. The intake is an unknown Performer with the multi/dual flange for spread-bore/squarebore. Looks like the one here.
    http://www.edelbrock.com/automotive_...ges/side_2.jpg

    The original Quadrajet had an adapter plate like this.
    http://www.holley.com/data/products/...medium17-6.jpg
    I left this off and bolted direct to the manifold.

    The truck is running great--fires right up, lots of power, no hesitation.
    My problem is a very high idle, even with the curb idle screw all the way out. I tried the trick of spraying carb cleaner at the base but-NO Change in idle. Do I need a sealing plate for this intake to run a square-bore holley? Thanks for any ideas guys.

    update===So Holley techs said it sounded like a vacuum leak, recommended the carb cleaner test, and to call edelbrock about needing a sealing plate for this intake.-----Edelbrock support said flat out "No you dont need a plate or adapter for that intake." I kept on , asking "what about older performers", but he seemed sure I didnt need a sealing plate.
    So back to square one- it seems.

  2. #2
    Join Date
    Dec 2009
    Location
    Ellington, CT
    Posts
    3,561

    Default

    Check to make sure the primary throttle blades are completely closing and that the secondary throttle blades are just about closed. Check the throttle linkage, make sure the primary shaft isn't somehow stuck on the fast idle cam (choke mode). Any plugs/caps left off or open on the carburetor/intake manifold?
    May God's Grace Bless You

    '78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, cold air induction, dual 3" exhaust/Magnaflow mufflers, 100HP progressive dry direct-port NOS, A/C, Lentech Strip Terminator wide-ratio AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, custom traction bars, 4" lift, 35" mud tires

  3. #3

    Default

    Hey thanks for the help.
    How do I see if the blades are closing--just look down into the throat of the carb?
    I did manually kick the chole fast-idle off. The idle drops down like it should---but it is still pretty high maybe 1200-1500 (no Tach). I have all the open ports covered with the caps that came with the carb.

    Oh, sweet truck on your icon by the way!

  4. #4
    Join Date
    Dec 2009
    Location
    Ellington, CT
    Posts
    3,561

    Default

    Quote Originally Posted by GMC4X4 View Post
    How do I see if the blades are closing--just look down into the throat of the carb?
    Yes, if the primary and secondary throttle blades are fully closed and the engine is still running on a high idle, then it's inhaling air in from somewhere else.
    May God's Grace Bless You

    '78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, cold air induction, dual 3" exhaust/Magnaflow mufflers, 100HP progressive dry direct-port NOS, A/C, Lentech Strip Terminator wide-ratio AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, custom traction bars, 4" lift, 35" mud tires

  5. #5

    Default

    So an update is in order.
    In the past two weeks I have :
    1.removed the throttle cable and trans kickdown---no change in idle speed
    2.installed a sealing plate between manifold and carb---no change
    3.checked to make sure the blades are closed---they are fully closed at idle
    so, Im running out of things to try here. Does anyone know if this could be timing/advance, or mixture screws will bring my idle down?
    I have been holding off on adjusting the mix screws due to the idle being too high---and my understanding is that Idle needs to be about right--then you adjust the mix for best vacuum.
    If anyone can help--Im thanking you for your time in advance---Thanks!

    I am going to double-check that I dont have any open ports on the intake--but I didnt change anything on the intake---just the carb.
    Last edited by GMC4X4; 11-24-2010 at 02:59 PM.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •