Blower set back pros and cons?

Discussion in 'InsideTopAlcohol.com Tech Questions' started by Compresser, Apr 8, 2019.

  1. Compresser

    Compresser New Member

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    When switching from a 10-71 to a 1471 HH blower I was told by manufacture I need a set back plate.
    This plate moves blower way back over distributor.
    I had to cut a large portion of the plate out to clear the distributor cap and wires as well as extend belt guard tensioner forward as well as with the extra height the blower belt barely fits.
    Cap and rotor are extremely close to underside of blower and blower must be removed to check rotor phasing and such.
    My question is this set back a good thing or just something to sell a $100.00 piece of aluminum?
    Thanks in advance.
     
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  2. greenracing

    greenracing Member

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    Depending on which HH blower and which manifold you have, the front discharge is ahead of the manifold opening unless you move it back, so in that case it's not an option. However you only need to move it back like 2 inches to get it lined up.
     
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  3. Mike Canter

    Mike Canter Top Dragster
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    On a high helix blower the exiting air/fuel comes out at a 45 degree angle towards the front. So unless the blower is set back the air has to make an abrupt 180* turn therefore the two most forward cylinders are getting high boost than the back ones. This is the real reason to set back a HH blower as far as you can to even out the boost on the rearward cylinders. Also you need to lay your blower on the bench upside down and lay your manifold on the top and check to see how much interference between the manifold front wall and the outlet of the blower. There should be none. If there is then for sure you got to move the blower back.
     
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  4. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    The only cons are making it all fit. Runs much better set back. It's not just a hp thing, it's hard to get the fuel system right with some cylinders hot. Without the right setback plate, the rear cylinders may get very hot at idle.
     
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  5. Compresser

    Compresser New Member

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    Trying to visualize in my minds eye what your describing here. I bought the intake, blower and plate all from the same company, so hopefully it was all engineered to work together.
    The plate thickness, does it have any performance advantage or disadvantage? My distributor cap and wires is very close to the bottom of the blower and I'm concerned about spark bleeding off to the base of the blower, as well as its a real bitch to check rotor phase after the blower is installed.
     
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  6. Mike Canter

    Mike Canter Top Dragster
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    Well you didn’t say that you had bought everything as a engineered kit but worth checking anyhow. Is all this on a Hemi or what? All the hemis run their plug wires close to the front of the blower. Just don’t bundle them tightly together. As far as rotor phasing if it is a hemi we use and offset mag drive to move it away from the blower.
     
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  7. Compresser

    Compresser New Member

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    Mike, this is a BBC setup.
    Everything came from BDS.
    I have been doing a bunch of reading via the search feature and have found that many racers are using the crab style cap to get more room under the blower.
    Also from the search I have determined I probably have two small of a vent and will be performing the glug test in the AM.
    I have a couple of more issues I want to discuss with you and the other experts on a new thread.
     
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  8. Mike Canter

    Mike Canter Top Dragster
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    You can also drive the mag off the front of the motor but that cost $$ to do but works well.
     
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  9. Compresser

    Compresser New Member

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    Mike, yes everything is pricy. I priced the front drive set up. Very nice, but hopefully I can spend that money more wisely on other parts.
     
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  10. Bjs344

    Bjs344 Member

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    As far as setting phase once you get the crank trigger style crab cap on there, mark the outside bottom of the cap under the #1 terminal and then transfer that to the distributor base. That way you can set phase with the cap off. In my door car now I have to put my phone on the top of the rear motor plate (under the windshield) and use the forward facing camera since the #1 terminal is all the way in the back (only way the distributor fits).
     
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  11. TADHemiracer

    TADHemiracer Member

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    Someone I know used a Dunn offset drive for a BBC motor years ago to clear the blower with his 44 mag. Might check out an offset distributor drive.
     
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  12. Dave Koehler

    Dave Koehler Member

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    As a chebby guy I can attest the Dunn offsets do work well.
    However, if you spend the money to move the mag up front you will never regret it.
     
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  13. Blownalky

    Blownalky Top Sportsman

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    I went through the whole scenario you are going through right now several years back. I had the crab cap with a BDS manifold and a 8-71 and changed to a 14-71 with a Indy manifold and a setback plate. The Indy was taller but with the blower hanging over it, it was still impossible to do anything back there. Assuming you're running something like a MSD Grid, 7, 8 or 10 with this? I was running a MSD 10 and I gave up using the crab cap for just the reasons you cited and I was worried about spark scatter with that small crab cap. I ended up getting a used Dunn offset and made an adapter to run the big Pro Mag cap and I ran this off the gear drive cover on the front where the fuel pump was driven. I left the pump in the center but I could move the offset around and with it the distributor head. I looked at the Jesel stuff and it just didn't fit the bill.
    I have it listed on this ad:

    http://www.insidetopalcohol.com/threads/all-kinds-of-stuff-for-sale-and-wanted.58495/#post-231307

    It's the Dunn setup with the wires. I don't have any pictures right now but I can get some later just so you can see what I did for an idea. The next line item is another option using a RCD 90 degree mag drive but of course you need to have a mag to go that route.

    https://www.facebook.com/photo.php?...zrAgLS1BwlzbHZWNWYI0oemKjmps0lkp-usmbU-CdoTTa
     
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  14. Blownalky

    Blownalky Top Sportsman

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    Here's some pics of the Dunn drive. A 5" Enderle fuel pump extension works great.

    [​IMG]
    [​IMG]
    [​IMG]
     
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