set back blowers

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by NITROBANDIT1, Nov 17, 2009.

  1. NITROBANDIT1

    NITROBANDIT1 LOST IN SPACE

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    see if i can get some good answers here. trying to set the blower back 2 inches on a hemi and wondering how much this should pick the hp up. obviously egts will be different now, which type blower would perform better by doing this, a 14-71 std or delta hi helix ? any idea if the jetting per cyl will be different? not asking for a tune up, but trying to get an idea of what will change and how much the tune up will be off by. alchohol fuel injected of course.adding also, since i dont see the psi screws setback, does that mean because of their weird discharge holes that they dont need it, or is their some kind of rule on this? due to the amound of money required to go 8-12 inch setback is why we are considering the 2 inch.thanks ita!
     
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    Last edited: Nov 17, 2009
  2. William Payne

    William Payne New Member

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    Good question , cant help myself because I honestly don't know . I will have to keep an eye on this thread I might learn something . Im not a racer or tuner but the set back blower thing I have found interesting for a while now . I don't know much about it will hopfully learn something here . From what I have read the way a roots blower works it forces more air to the front of the engine then the back apparently tuners would counteract that with different compression ratios in the front compared the back and running some cylinders leaner and richer then others and that the setback deal allowed the engine to get evenly distributed air allowing tuners to keep all cylinders relatively the same . I have no idea if thats true but with how an internal combustion engine works the theory sounds right . Hopfully this thread will educate me on whether im right or whether I have read a load of crap .
     
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  3. secondwindracing

    secondwindracing top alcohol

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    well here it goes:) we put a set back hi helix on at the last race of the year and the car really woke up..big time...left the same tune up in it and I did notice that #1 and #2 showed more heat on the plugs and #7 and #8 was cooler so now I'am going to pinch down 7 and 8 and fatten up 1 and 2..but I did see a big change in the car proformance.to sume it up...very HAPPY..Dave
    www.myspace.com/daveloweswr
     
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  4. craig moss

    craig moss Member

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    From what I have been told moving the delta/retro opening to the center of the intake lets the blower beat up 4 cylinders instead of the just the front 2. It just helps equalize the boost /fuel between more cylinders. I would love to have a 12 inch snout to do this. Anyone have one for a roots ?? :confused:
     
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  5. Money Shot

    Money Shot Member

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    set back

    I actually had a sheet metal intake made that has the opening directly in the center. My port jets are square and needed no offset. Perfect fuel distribution. I used a 8 inch snout modified to fit my SSI 14/71 HH. Works very well. Mine is a 565 BBC w/Big Chiefs. Good Luck :cool:

    Randy
     
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  6. Big Sexy

    Big Sexy Member

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    Moving to a setback is intended on evening out the nozzles and boost. At first, you will more than likely stir your nozzles, and need to make changes. The HP increase is a result of making the boost more "equal" from where it is today. I have been told that if your nozzles are close today, and you have your car "figured" out. It may not add a significant increase in performance.
     
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  7. SoDak

    SoDak Active Member

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    Last time I checked with SSI, the 12 inchers were about $1800. I would think there is a less expensive place than that but I don't know where.
     
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  8. M Tigges

    M Tigges TAFC

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    Intake mods (high helix)

    Do not think 2 inches will do anything! We used a shoe deal in the manifold that got us away from short rods in 1 and 2 and distribution was better. Always wanted to build our own sheetmetal intake to center the blower like the fuel guys do now. But now we have this new Cuisinart and the outlet is now in the rear!

    Mark
     
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    Last edited: Nov 18, 2009
  9. SoDak

    SoDak Active Member

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    please explain your "Cuisinart":eek:
     
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  10. M Tigges

    M Tigges TAFC

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    Screw blower Dude!
     
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  11. topalky511

    topalky511 Member

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    I ran a 451 bae with fathead 5's a couple of years ago with a 1671 hh retro, without different rod lengths it used to beat up cyl 1 and 2 , then i moved it back, had an 11" snout made then it just beat up cyl 3 and 4 instead, i really dont think you will see a real gain with setback unless you have a proper manifold , just like the fuel guys run
     
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  12. secondwindracing

    secondwindracing top alcohol

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    Tiggs...do you have a pic of the shoe you used..also if you know anyone that wants the bead locks send them my way I had 51/2 bolt circle:confused:..as far as my blower the set back is only 2 in...Dave
     
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  13. Mike Canter

    Mike Canter Top Dragster

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    There is no doubt that moving a Rootes HH blower back will help. The further back you move it the more it will help. I have to agree that moving the blower back two inches will not help a lot but maybe some. The problem with the HH Rootes is that the exit angle of the air out the pie hole is steep. Probably around 40-45* angle right towards that front burst panel and thus that is why the exit hole is shaped like a slice of pie. Given this you can see why moving the blower back just a little doesn't help a whole lot. The standard blower is not that steep but it still comes out at a a slight angle. To really take full advantage of setting the blower back you need to go way back like the Top Fuel cars.

    A screw blower exit air is not as steep and I believeit comes more out of the back of the blower.
     
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  14. underby6

    underby6 Active Member

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    Mike is correct, moving it back is a huge plus to even out the cylinders. The big disadvantage is the $3000+ snout, $5000 custom intake, and another $1k in supports and what not from RCD. From what I have seen you need at least 10-12" of setback. We considered doing this on our small block setup when top fuel first started doing it. The cost vs. performance gains just weren't great enough. The Kalitta's used a shoe inside the intake and this worked very well for them. This was done for the same performance reasons, and the fact that AJ wasn't producing them in masses at the time. You might check with Robert Rheel or Holbrook and see if they have one. Simple solution....throw a screw on it and have all the power you could ever want. Or if you really want to save money make it into an injected nitro car....that will save you the most $$$:D

    Brandon Booher
    NHRA TAD #44
     
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    Last edited: Nov 20, 2009
  15. d.kirkalkyburner

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    mike and Brandon

    Mike arent yje fuel cars std. rotor? So there angle isnt as much yet they set the blower 7-9 inches with longer than std. snouts so this would still work with std. rotor deals on alcohol? thanks
     
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  16. Mike Canter

    Mike Canter Top Dragster

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    Yes, as I said in the previous post, a standard rotor still has the exit air coming forward at an angle but just not as steep as a high helix rotor. The problem is with a HH is that the air is pushing forward at such a steep angle that it goes into that burst panel pocket then has to reverse its flow 180 degrees to get to all the other cylinders. This is creating massive amounts of turbulence. Shoes work great on a standard rotor because that angle is not so steep but they don't work as well with a HH rotor. Never tried it but it would seem to me that with a HH a shoe and a set back would be the best combination.
     
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  17. underby6

    underby6 Active Member

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    On the shoe topic, the fuel teams mounted theirs at the very front of the intake. The shoe was basically touching the back of the manifold. We had to move ours around and eventually we ended up with it 2" or so away from the front. This is because, as Mike stated, the path at which the air exits the case on std. vs. H.H.. A setback is def. better, it just depends on how deep your pockets are. I know Rob Atchison worked with a customized roots setback design, and had a very very good setup. I'm sure several other IHRA TA/FC guys did as well, Rob was just pitted next to me at the Bowling Green D3 Race and I saw his. Perhaps you could get in contact with him, I personally don't have his contact info.

    Brandon Booher
    NHRA TAD #44
     
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    Last edited: Nov 21, 2009
  18. LeWhite

    LeWhite BB/Alt

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    ?

    HH moves the air forward slower.
     
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  19. Don Onimus

    Don Onimus New Member

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    oilers

    I have a set of williams valve covers with a set of -5 fatheads. Can I put a set of spray bars for the intakes or who should I call for a set? Thank you Don Onimus donimus333@yahoo.com
     
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  20. RUGSTER

    RUGSTER New Member

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    10" Billet snout.

    I had a guy here in OZ make a 10" snout with Three bearings in it to set my H/H 14 back so the front of the pie is directly in the centre of the manifold. I have had it running however i haven't had time to test the car:rolleyes:
    How the thing was going to work with the blower in the standard position with say a 3 7/8" snout i'll never know:confused:
    Just a note: he charged $1000.00 AUD for the snout, with the tag for a turn buckle to support it on the front. It has a 4340 shaft.
    Jason:)
     
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