How much boost should I expect?

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by gt_diesel, Jun 25, 2009.

  1. gt_diesel

    gt_diesel New Member

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    Just a side note... I know at my track, they limit OD to 20% in top sportsman which is the class I will be running.
     
    #21
  2. Bottlefed

    Bottlefed New to Blowers

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    Std. vs HH

    My understanding is that the standard helix works pretty well at low overdrive/rpm and that you really don't see a lot of benifit from the 120* twist till about 7500 and up. Is this correct or bad information?

    Richard Gavle
     
    #22
  3. Mike Canter

    Mike Canter Top Dragster

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    I think you have it backwards. When the limited Promod to 20% OD then a lot of racers started eyeing the standard blower to get more boost but then NHRA woke up and limited it to high helix only.
     
    #23
  4. Bottlefed

    Bottlefed New to Blowers

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    Thanks for the reply Mike,

    If you reread my post, that is what I was saying. That the Standard twist rotor works good at low speed and the High Helix needs to be spun fast to show its advantage.

    Thanks again for the reply.

    Richard Gavle
     
    #24
  5. Mike Canter

    Mike Canter Top Dragster

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    Sorry Richard. Yep thats what you said.
     
    #25
  6. afuel141

    afuel141 New Member

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    Are you talking about NED?? There is no such rule in Top Sportmans there
     
    #26
  7. gt_diesel

    gt_diesel New Member

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    Yeah, NED.... I was thinking they went by the IHRA 20% rule...
     
    #27
  8. sune

    sune Member

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    Well i wont pretend to know anything as im still new to blown alky cars myself.

    I will give you some input from my setup tho, it is very similar to yours:

    this is my setup:

    cbb 555

    14/71 std helix littlefiled striped fairly fresh running at 11.1% od

    11:1 static compression

    just under 0.800 cam

    buzzardcatcher

    doorcar, powerglide.

    this produces just under 25 psi in the current setup
     
    #28
  9. Mike Canter

    Mike Canter Top Dragster

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    Sune, at what RPM do you see just under 25 lbs of boost?
     
    #29
  10. sune

    sune Member

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    at idle it sits at about 10 - 15 psi.

    max boost is reached at 7500 - 8000 rpm
     
    #30
  11. RUGSTER

    RUGSTER New Member

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    Aahhh...... WHAT?????? 10-15 at idle??? i'm lost:eek:
    Jason.
     
    #31
  12. Kevin O'Dell

    Kevin O'Dell Member

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    Are those readings coming from a gauge or a datalogger? I had an autometer gauge that read 10 psi when the car was off and would bury it at 50psi during a run. Installed a racepak shortly after and less than 40psi during the run was recorded.
     
    #32
  13. sune

    sune Member

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    those are from a gauge, i don't have a datalogger installed
     
    #33
  14. SCO1035

    SCO1035 New Member

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    Just replaced my guage for exactly the same reason!
    Racepak one day!!
     
    #34
  15. SoDak

    SoDak Active Member

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    Long time ago we ran BBC 540's, 10.5:1, large rect. port Chevy heads with std helix LF 8's at 45% over. We would run about 6500-7000 RPM and make about 15-20 lbs boost.
     
    #35
  16. gt_diesel

    gt_diesel New Member

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    Just an update... we ran 26 pounds of boost at 6800 rpm at 20% over.
     
    #36
  17. Mike Canter

    Mike Canter Top Dragster

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    That is good. A lot better than running 1 to 1. Congratulations;). Was everything else OK
     
    #37
  18. gt_diesel

    gt_diesel New Member

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    The track was pretty bad.... We blew the tires off on the line, got on and off the gas, shifted at 6500 and coasted thru the traps with a 5.33 @ 101 mph.

    That was letting off around 500 feet
     
    #38
  19. hotrodharlkey

    hotrodharlkey New Member

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    what top and bottom pulleys you running?build a engine close to you..was told my heads will flow in that area of 400..my cam is smaller..a 746 lift..piston bigger at 11.5--to--1..running a std. rotor 12-71 blower that littlefield just fresh up for me.
     
    #39

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