Valve spring selection

Discussion in 'General Engine Discussion' started by Joump5, Jul 20, 2019.

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  1. Jul 20, 2019 #1

    Joump5

    Joump5

    Joump5

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    Anyone know of a rule of thumb for
    calculating valve spring size/spring
    rate for a small gas engine? Any
    advice on selecting or sourcing
    springs?
     
  2. Jul 20, 2019 #2

    Brian Rupnow

    Brian Rupnow

    Brian Rupnow

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    If it is a model engine with cam operated exhaust valve and atmospheric intake, use a spring of 0.022" wire diameter for the exhaust and use a spring of .012" wire diameter for the intake. as a generalization the outside diameter of the spring should be about 1/4".
     
  3. Jul 20, 2019 #3

    WOB

    WOB

    WOB

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    The important thing is to get the proper spring force. For the size of engines usually made by hobbyists( valve head under 1/2"), 2 lbs compression when installed with a max of 3 lbs. will do the job 99% of the time. A good source of springs is mcmaster.com.

    WOB
     
  4. Jul 20, 2019 #4

    stevehuckss396

    stevehuckss396

    stevehuckss396

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    Grainger.com has a HUGE selection of compression springs. I just ordered springs for a project. You can have them sent to a store if there is one near you and save the shipping. I have one about 6 miles from me.
     
  5. Jul 21, 2019 #5

    Joump5

    Joump5

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    It will actually be a relatively large engine. 2” bore.
    Both valves operated by cam, pushrod,rocker.
     

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