Our Tomahawk refresh

Discussion in 'Race 400/430/455' started by slimfromnz, Jan 20, 2016.

  1. slimfromnz

    slimfromnz Kiwi Abroad

    As some of you may know, we have rebuilt our 555 with more compression. We went from 12:1 to 13.5:1.
    Before we made 832hp and 785ft/lb
    Today we made 909.9hp and 835ft/lb


    So happy considering the lack of cam and head
  2. Robs455

    Robs455 Well-Known Member

    Congratulation these numbers are impressive!
    Can you tell more about your upgrade from 12:1 to 13.5:1, whats your dynamic compression rate now?

  3. Jim Weise

    Jim Weise EFI/DIS 482

    Congratulations Royden, I know that 900 was your goal all along.. always feels good to make that.

  4. sriley531

    sriley531 M.M.O.G.

    Awesome machine Royden!
  5. StagedCat

    StagedCat Platinum Level Contributor

    Very impressive!! Same cam?
  6. Smokey15

    Smokey15 So old that I use AARP bolts.

    I can see where more cam would kick up the power by the RPM where it peaks. Still, that Tomahawk will do some serious scalping!
  7. DaWildcat

    DaWildcat Platinum Level Contributor

    I couldn't be happier. Looking forward to a ride next time I'm there.

  8. slimfromnz

    slimfromnz Kiwi Abroad

    Thanks Guys.
    The only parts we changed, were the rods and Pistons.
    I will have to calculate the dynamic compression
  9. slimfromnz

    slimfromnz Kiwi Abroad

    Running E85, the compression originally was too low. We had fuel wash in the bores when it wasn't at WOT, which on the street, isn't much. Changed to a high tech Diamond piston with a fancy ring package and longer Callies steel rods. The rods are 7.1" long. The compression height was changed to get the pin closer to the top ring to give better piston stability.
  10. Smokey15

    Smokey15 So old that I use AARP bolts.

    If you are getting fuel wash in the cylinders under cruising, your carb is the problem. Whose E85 carb are you running? Watch you oil closely for contamination. Level may stay the same if the engine always gets fully up to temp, because it will burn off. I heard of an engine that needed a rebuild after an issue with a poorly built E85 carb.
  11. slimfromnz

    slimfromnz Kiwi Abroad

    Carbs are ProSystem units.
    My engine guy told me it was the lack of complete burn in the chamber and that bumping the comp up would help eliminate it.
    Check out the BSFC on the dyno chart. We could have trimmed it out, but we were happy where it is.

    It amazed my engine builder, how this motor was responding to timing. We would only add 2' timing each run and we gained 20+hp on each pull right up to 900hp. We didnt even change any jets, bleeds etc just added timing.
    I may have even converted my engine guy


  12. Smokey15

    Smokey15 So old that I use AARP bolts.

    PM sent.
  13. gmcgruther

    gmcgruther Well-Known Member

    Royden, you should check out Dart Machinary and Darin Morgans articles on fuel wash. Its the opposit, they discovered what we all thought was fuel wash is actually a complete fuel burn because of where the multiple vortexes are after coming out of the cylinder heads. Look at Darts and Darin's wet flow area, you will see and read what I have learned. Becareful on your E85, test it every time you get a new batch. There has been reports of low amounts of alcohol in some cases. Way to go on the 900+ hp mark. Proud of you.
  14. gmcgruther

    gmcgruther Well-Known Member

    Royden, your carbs are not that far off, I promise you that. ProSystems are second to non for carbs, only one other company has challenged them, a Gary "Williams" carbs. Thats there is a bold statement. If I had you engine, I would of went to 14.5:1 compression ratio, the E85 loves high compression. Our local round-a-round "circle track runs mainly E85 and 14.5:1 to 15.5:1 compression and they scoot pretty good. I love it when in the I.M.C.A. unlimited class, the Buick engine guys smoke everything in site.
  15. m louk

    m louk Well-Known Member

    Nice up-grade for hp, do you have video of the dyno run?...........Mike
  16. slimfromnz

    slimfromnz Kiwi Abroad

    Here you go
  17. slimfromnz

    slimfromnz Kiwi Abroad

    Sasha455 likes this.
  18. m louk

    m louk Well-Known Member

    Ahhh nice :TU:, bet you could feel it behind the wall.
  19. slimfromnz

    slimfromnz Kiwi Abroad

    Yes we could. The videos never do it justice.
  20. flynbuick

    flynbuick Guest

    What is the new power to weight ratio?

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