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Thread: how much valve spring psi?

  1. #1
    blownzoom440
    i need to change my springs with running more boost.
    how much more psi do i need?
    1.88 install height[1.9w/shim .020]
    1.0 width double with damper,.700 inside diamater.
    2.14 Stainless valve.3.2sq in area.
    14lbs of boost
    6800 rpm
    the prior spring had 180psi seat,300psi open at .550 lift with 8lbs of boost.
    sorry if i forgot any info.just ask if so.
    thanks for any help!!
    i was looking at the comp 938 w/480lbs in.
    bind at 1.225"
    i think it gives me 220lbs on the seat.
    http://board.moparts.org/ubbthreads/...Number=2822511

  2. #2
    Junior Member
    Join Date
    Jul 2011
    Posts
    594
    basically you take the sq. of the valve and multiply by the boost, and that is how much more spring you need. My calcs say your valve has 3.59 sq. in which means you 59 more lbs. I'd say 40 is close enough and with a flat tappet you don't want to go over board and flat'n da cam

  3. #3
    Fiat48
    I assume this is a roller cam?

  4. #4
    blownzoom440
    I assume this is a roller cam?
    no it iis a solid tappit.252/260 at .050 .541/.559 lift comp cam.i was thinking about the cam taking more spring psi is it was gunna be real bad for it.

  5. #5
    Junior Member
    Join Date
    Jul 2011
    Posts
    594
    no it iis a solid tappit.252/260 at .050 .541/.559 lift comp cam.i was thinking about the cam taking more spring psi is it was gunna be real bad for it.
    At that spring pressure the chances of your surviving are about nil. get your self some comp. barrel springs for a big block and be happy, but with that kind of boost I would think that you were running some full boat deal

  6. #6
    steelcomp
    Time for a roller. You can't have your cake and eat it too.

  7. #7
    DetroitJim
    Yikes! comp 938's will kill your cam. 204 lbs. at 1.900 is roller territory. I'm surprised you haven't wiped your cam already if you have 180 lbs. now.

  8. #8
    blownzoom440
    At that spring pressure the chances of your surviving are about nil. get your self some comp. barrel springs for a big block and be happy, but with that kind of boost I would think that you were running some full boat deal
    i am not aware of barrel springs!?
    do you have a part #?
    i will call comp to check the max psi thay allow for spring psi.
    thanks for the help so far!!!!

  9. #9
    blownzoom440
    so thay said what i have is the max at 180# seat psi.i had to check to be able to compare to.
    i must be getting spark crossfire in the cap or have bad plug wires.
    the engine is not firing all the time and shook the car on the chassis dyno.i believe it is effecting all cylinders because when i took it apart to upgrade the crank all the chambers/pistons looked the same[good condition]AH HELL!
    it is a long story to tell getting where i am now with this.8 lbs and up she no workie as soon as you hit the gas!!!
    .020 plug gap NGK #8
    7AL-2 MSD/pro coil,billet distr.

  10. #10
    DetroitJim
    Go through your entire ignition, check for arcing or plug wires. i would open up the plug gaps, 0.040 to 0.050 is fine for an MSD. Also check all of your ground wires back to the battery. if you are going through any anodized aluminum to get there, it can cause a problem.

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