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Technical GM dual throttle return spring question

Discussion in 'The Hokey Ass Message Board' started by Hotrodjohn71, Mar 6, 2021.

  1. Hotrodjohn71
    Joined: Feb 25, 2018
    Posts: 37


    What is the reason for the dual throttle return springs on the 60s and 70s GM engines? Where there is a large outer spring with a smaller inner spring. Is this just a safety feature in case one of the Springs breaks?
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 47,962


    I think so.

    Sent from my Trimline
  3. Russco
    Joined: Nov 27, 2005
    Posts: 4,167

    from Central IL

    I assume so, 2 return springs are required for many sanctioning bodies for racing as well.
  4. I had a factory spring where one wire was folded in half, then the double strands were wound into the return spring.
    Safety inspector tried to say it was not double. It removed it so he could see the two strands up close.
    Deuces and Hotrodjohn71 like this.

  5. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,169

    from illinois

    Just guessing but I'll bet it had more to do with spring rate , as the springs were different shapes & wire sizes ...
    winduptoy, Deuces and Hotrodjohn71 like this.
  6. harpo1313
    Joined: Jan 4, 2008
    Posts: 2,121

    from wareham,ma

    Backup spring, a very good asset.
    Deuces, Hotrodjohn71 and tractorguy like this.
  7. borderboy1971
    Joined: Oct 20, 2008
    Posts: 744

    from Canada

    I used to do safety inspections. It is written in our vehicle standards act. Yes for safety reasons in case one breaks. I'm sure other jurisdictions have different regulations though.
    Deuces and Hotrodjohn71 like this.
  8. poco
    Joined: Feb 9, 2009
    Posts: 447

    from oklahoma

    I was a inspecter for nsra and dual throttle springs were mandintory.
  9. jimmy six
    Joined: Mar 21, 2006
    Posts: 8,516

    jimmy six

    SCTA-BNI was the same. But some inspectors had a funny way of counting. You could have ten springs and count each one and some of them would want one more. By the way shaft springs never counted even if they were on each side....
    Tman, Deuces and Hotrodjohn71 like this.
  10. saltflats
    Joined: Aug 14, 2007
    Posts: 10,611

    from Missouri

    Thought that was a D.O.T. thing, not sure what year it started.
    Deuces and Hotrodjohn71 like this.
  11. I too was on a NSRA safety inspection team, that's something they look for, it is a safety feature if a spring was to brake the other will keep the throttle from going past center is what I remember as the reason for the 2 springs. HRP
    Deuces and Hotrodjohn71 like this.
  12. 325w
    Joined: Feb 18, 2008
    Posts: 5,505


    Yep still in the book. One inspector was wearing a guy out about not having a spring one day.
    Was able to show the lead inspector how recognize a GM throttle body. Late eighties vintage.
    Deuces and Hotrodjohn71 like this.
  13. mcsfabrication
    Joined: Nov 26, 2006
    Posts: 920


    Cheap insurance.
    Hotrodjohn71 and Deuces like this.
  14. Deuces
    Joined: Nov 3, 2009
    Posts: 19,731

    from Michigan

    Holleys have a primary spring that are wound up over the throttle shafts...
    Last edited: Mar 7, 2021
    Hotrodjohn71 likes this.
  15. jimmy six
    Joined: Mar 21, 2006
    Posts: 8,516

    jimmy six

    Not countable with racing organize ran with even though I’ve shown the inspectors that with all other springs removed and the throttle rod or cable attached or not, at wide open throttle held by hand, let go, the butterflies slam shut.... still a no go. 2 additional springs or go home.
    Hotrodjohn71 likes this.

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