Valve spring seat pressure ?

Discussion in 'High Performance Modifications' started by slamdik, May 7, 2010.

  1. slamdik

    slamdik Member

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    I just ordered a hyd. roller for my 400 from Howards.

    The guy from Howards says 135-140 on the seat,so I call AFR(I'm running AFR heads) to see what they recomend to get that.AFR asks for the cam specs and he tells me 150 on the seat(Comp 977).

    Cam will be on a small base billet core.

    242 248

    545 565

    What do you guys think?

    Thanks

    Sean
     
  2. Damon

    Damon Veteran Member

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    With a roller you can put more seat pressure on it without any really bad effects. It's the pressure over the nose of the cam that seems to be the weak link for a hydraulic roller- it can be a balancing act between the aggressive ramps possible with a roller, the springs necessary to control those acceleration rates at high RPMs but limited by how much pressure you can put on the guts of the hydraulic lifters before it causes problems.

    If you're buying a fully assembled head from AFR then I'd go with their recommendations. 10 lbs. difference on the seat isn't going to matter much.

    If you're buyign springs and spec'ing the heads out yourself maybe consider some appropriate beehives. They can solve a lot of issues with hydraulic roller cams like good vavle control without resorting to monster spring pressures.
     
  3. 70RS_L48

    70RS_L48 Veteran Member

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    +1

    AFR's recommendation is good. Beehives are better though. Either that, or consider a rev-kit if you're planning on going above 6000rpm.
     
  4. Tokyo Torquer3

    Tokyo Torquer3 Veteran Member

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    I would go with the AFR recommendation of 150#, but no more as much more than that will overcome the hydraulic mechanism in the lifter at low rpms/oil pressure. Get a good set of lifters. I usually aim for 140-150#. I tried 175# on a set of morel lifters but it was a bit too much seat at low rpm.

    I have tried it all.. Beehives, Hydra-rev kit, etc. Do not waste your time with a rev kit on a hydraulic roller. did not help me one bit and was a PIA. They help with solid rolers with aggressive lobes. Beehives and titanium retainers can help you find a few more rpm.

    mike
     
    Last edited: May 8, 2010
  5. ZS10

    ZS10 Moderator Staff Member Lifetime Gold Member

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    Higher seat pressure, for sure.
     
  6. slamdik

    slamdik Member

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    Do you think Howards said 135 because it would have been on a cast core if I didn't order it billet?
     
  7. Tokyo Torquer3

    Tokyo Torquer3 Veteran Member

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    you will be OK with 150# seat pressure with a roller and a cast core, regardless. Just make sure your open pressure is under 400# on the cast core.

    mike
     
  8. slamdik

    slamdik Member

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    Sorry for the confusing post. I DID get it on a billet core.

    The springs AFR recomended were Comp 977 150# on the seat 420# open.
     
  9. Tokyo Torquer3

    Tokyo Torquer3 Veteran Member

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    your open pressure will depend on your lift. good to do the calcs.

    don't forget the bronze tipped fuel pump pushrod (if mechanical) and the special distributor gear if you didnt have an iron gear pressed on the cam.
     

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