valve spring question

Discussion in 'Race 400/430/455' started by race0, Jun 25, 2020.

  1. race0

    race0 Active Member

    Going to the dyno soon, and want to test a solid flat tappet cam vs a hydraulic roller.. the heads are currently set up for the roller, 160 lbs on the seat and roughly 400 lbs open.. I really don't want to change valve springs on the dyno if I don't have to.. Has anyone ever run this much spring pressure with a flat tappet cam.. It will be a few dyno pulls only, and the cam is already broke in and peak power in the past with the flat tappet cam was 6500 rpm. Thanks in advance for any input. Timmy
  2. Bens99gtp

    Bens99gtp Well-Known Member

    What are cam specs?

    I think in a lot of more aggressive solid flats it's not uncommon to see 350+ open pressures.........if the cam is big enough to require that I don't see 50 psi more for a few pulls going to eat anything up.

    I know my are so stiff when manually rolling it over it's a workout
  3. Stevem

    Stevem Well-Known Member

    160 is too high to break in a flat tappet Cam with the diameter of the lifters used!

    If it was a Chevy or Ford with Mushroom lifters, or a Mopar with there big lifters it would be a different story!

    I would not want to see more then 140 psi, and even with that pressure I would be sure to add a bottle of LUCAS oil products racing ZDDP additive.
  4. Bens99gtp

    Bens99gtp Well-Known Member

    OP said cam was broke in already ???
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  6. standup 69

    standup 69 standup69

    I ran k motion k800 springs on a solid 508 for years 180 seat almost 440 lbs open lived fine ..ran the same springs on a 304 solid
    Should be ok
  7. race0

    race0 Active Member

    Thank you for all the replies, as mentioned above the cam is already broke in.. I have used this cam for a while with great success but I have always wanted to drive it to the track and run in the 9's, full weight, tailpipes, etc.. It's been 10.0s and since i'm putting the engine back together I figured while I had it on the dyno I would see which one makes the best average power. I already know I need more stall speed so now would be a good time to try this comparison. Thanks again Timmy
  8. alvareracing

    alvareracing Well-Known Member

    you should have no issues, I've ran last motor with 165 close and 370 over the nose, on a solid flat tappet. We (machinist and I)believe in slamming the valve shut and never an issue with valve float. 58 1/4 mile passes with that set-up with no excessive wear on cam or lifters, even using oil restrictors to the lifters.
  9. race0

    race0 Active Member

    Thanks for the reply Fernando, if you don't mind me asking, what brand solid lifters are you running?
  10. alvareracing

    alvareracing Well-Known Member

    wow, I am 90% sure they were Melling. Nothing special a basic .842 small block Chevy application solid lifter. Never had a single problem, motor would run thru the traps a 7100 with no issues. Except my butt cheeks were puckered up spinning the motor that high, but damn it would go there without a beat. Over the winter I will be doing another solid lifter motor for my 71 and I will be researching this lifter subject more carefully. One thing I did read was that Melling is offering a .005 oversize lifter, which caught my attention because we can control the hemorrhaging between the lifter and the bore a lot easier. Ever since we have been focused on that, and restricting oil to the top, we have had great success with oil pressure and keeping bearings looking like new for a long time.

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