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valve spring presure for blown 392

Discussion in 'The Hokey Ass Message Board' started by imperial, Feb 26, 2006.

  1. imperial
    Joined: Feb 14, 2006
    Posts: 63

    imperial
    Member

    The standard springs in the 392 are 88 lbs closed 184 lbs open.
    Now with the 6-71 I need a bit stiffer springs.
    what would be a good valve spring pressure for this @ about 14 psi boost
    Thanks remco
     
  2. FEDER
    Joined: Jan 5, 2003
    Posts: 1,261

    FEDER
    Member

    Your spring pressure will be determined by the camshaft You use. Do You have the cam specs? What cam are You using? FEDER
     
  3. Bugman
    Joined: Nov 17, 2001
    Posts: 3,485

    Bugman
    Member

    What he said. Your cam supplier should be able to recommend a spring for you.
     
  4. Take the area of the valve in square inches times the amount of boost. You need to add this to the seat pressure of the spring. Now the problem. If you have more than 120 lbs. of seat pressure on any flat tappet cam, you will knock of the lobes in short order. You're one step away from why they made hard faced overlay camshafts. If you run a roller, you don't have to worry about that . The other thing is how much rpm are you planning on running? If you run 4500, you can runaround 120 lbs. on the seat and be ok. If you want to turn it above 6 grand, you're going to have to have serious springs because of the weight of the valve train. If you don't have enough pressure and you float an intake valve, you'll see your blower head off into orbit.
     
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  5. Bugman
    Joined: Nov 17, 2001
    Posts: 3,485

    Bugman
    Member

    Have you concidered beehive valve springs? Less seat pressure while allowing higher RPMs by reducing the weight of the spring and the retainer. I'm sure Crane or Comp could come up with something that would work.
     

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