Valve Float

Discussion in 'Mopar Performance Issues' started by dibbons, Dec 19, 2017.

  1. dibbons

    dibbons Well-Known Member

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    When a hydraulic lifter cammed motor experiences valve float, how far open are the valves when this happens?

    Do both intake and exhaust valves float at the same time or do the heavier intake valves always float first?

    When does this condition cause contact between the piston dome and valve face? Thank you.
     
  2. SGBARRACUDA

    SGBARRACUDA ROY FABO Gold Member

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    Weight of the valve components and mostly worn out springs are the cause of float. Since the intake weighs more, than yes it is the one that will float first.
     
  3. SGBARRACUDA

    SGBARRACUDA ROY FABO Gold Member

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    Pretty good video here showing what it looks like.
     
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    • SGBARRACUDA

      SGBARRACUDA ROY FABO Gold Member

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      Pretty neat to see the valve rotating after the valve is on the seat. ( towards the end)
       
    • JBurch

      JBurch Well-Known Member

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      When the pistons and the valves try to occupy the same space at the same time
       
    • IQ52

      IQ52 Well-Known Member

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      When the valves float, or the lifters pump up as they launch over the closing ramp, it is generally the exhaust valve that hits, as the piston is coming up towards the exhaust valve when it is being held open, and the piston is going down away from the intake valve if it were floating. Yeah, I think I remember that right. Haven't thought about it for awhile.
       
    • moper

      moper FABO Gold Member FABO Gold Member

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      ^^ What he said.
       
    • Max1196

      Max1196 Well-Known Member

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      ^^ what he says and him too! Piston chases the exhaust valve shut OR maybe it catches up to it! 100_1428.JPG
       
    • AJ/FormS

      AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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      If this happens to you with a 318 you will hear it right away. And Then there's is a real good chance it won't idle, so keep the Rs up and get it on home.
       
    • Tooljunkie

      Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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      Stolen chevy right on the carpet in 1st gear,buddy recovered his truck (engine was still hot,guy was bleeding on the ground) and i had the (dis) pleasure of tearing it down. Found pieces of piston in the air cleaner. Yup it was toast. When we overhauled it months before,never considered floating valves at the time....
       
    • BigBlockMopar

      BigBlockMopar BigBlockMember

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      Valves start to float when the springs can't control them, or themselves, anymore.
       
    • acpat

      acpat Well-Known Member

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      valve float or lack of compression ? what is compression of motor ?