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Thread: Throttle shaft repair Holley 4150 (4801-1) 780 cfm.

  1. #1
    Join Date
    Mar 2019
    Location
    France - Paris area
    Posts
    4

    Default Throttle shaft repair Holley 4150 (4801-1) 780 cfm.

    Carb Ref: 4150 model 4801-1 (on a 1971 Corvette LT-1, 780 cfm, 780 vacuum secondary)
    Hi. The throttle shaft on the passenger side, where the choke is located, is too loose, as the hole is worn. I can't lower my idle speed more than 1000-1200 RPM (even with the secondary stop screw unscrewed). I have an air leak, and the air is clearly going through that worn hole (tested with start fluid spray right on the hole and RPM is decreasing immediately). I need to drill the throttle base plate and insert some brass bushings. Looks like a deja vu procedure for many people. I have some questions in order to do it properly and order the right stuff at first (I'm in France, and I'm loosing 2-3 weeks for each order): - I saw some repair kit with bushings with an internal size 3/8" (exterior/drill size is 7/16) Will this kit match my carb throttle plate? - While I'm in it, I may renew the shafts (primary + secondary) the plates, and screws. What refs would match my carb. (My plates are stamped 172). It's hard from France to get stuff from U.S. and less easy to send them back (freight costs). Last suggestion, if one of you has found a replacing plate I'd take this advice too. There are no new 4801. And they cost three times the price of a brand new equivalent. List # is matching my car and I'd like to keep it. Thank for your help. Michaël

  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    2,197

    Default

    Strange the choke side is more worn. I do my own, but you MUST use a kit with a piloted reamer like this:
    https://www.ebay.com.au/itm/23296917...IaAngjEALw_wcB. Do not rebush the secondary, only the primary side. Fit the nylon ribbons to the secondary side. Gary
    Regards, Gary

  3. #3
    Join Date
    Mar 2019
    Location
    France - Paris area
    Posts
    4

    Default

    Thank you Gaz64 for your prompt reply. You're right, usually it's the opposite side that get wider due to the throttle cable force. I had a crack on the passenger side (over-torque probably) and the welding job as widened the hole around 0.02", enough to have that whistling vacuum leak.

    I saw the same kit in 3/8" (you're confirming as the good one) at carbjunkys. My concern is: What will arrive soonest in Paris France
    Otherwise, I have a PTFE teflon sheet, I can cut very accurately with a scalpel, to fit the shaft grooves. Well thank you for your contribution. Have a good day.

  4. #4
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    2,197

    Default

    I'm in Australia, and have bought this kit and other parts from carbjunkys. Shipping time is fairly reasonable. You might find similar kits closer to you. Gary

  5. #5
    Join Date
    Mar 2019
    Location
    France - Paris area
    Posts
    4

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    :thumbup1: :thumbup1: Thanks for all. Australia is a long way from Paris! Take care my friend.

  6. #6
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    2,197

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    And same back to you.
    Regards, Gary

  7. #7
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,917

  8. #8

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    @Gaz64: We'll take as reference when we start working on the Holley 4150. Need to first finish the installation of the rack and bakflip cover on the truck before we can clear the garage.

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