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Old 02-26-2006, 04:41 PM   #1
imperial
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Default valve spring presure for blown 392

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
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Old 02-26-2006, 05:22 PM   #2
FEDER
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Default Re: valve spring presure for blown 392

Your spring pressure will be determined by the camshaft You use. Do You have the cam specs? What cam are You using? FEDER
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Old 02-26-2006, 05:32 PM   #3
Bugman
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Default Re: valve spring presure for blown 392

Quote:
Originally Posted by FEDER
Your spring pressure will be determined by the camshaft You use. Do You have the cam specs? What cam are You using? FEDER
What he said. Your cam supplier should be able to recommend a spring for you.
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Old 02-26-2006, 05:33 PM   #4
wfo guy
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Default Re: valve spring presure for blown 392

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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Old 02-26-2006, 07:28 PM   #5
Bugman
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Default Re: valve spring presure for blown 392

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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