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  1. #1

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    03 xlt 1390 with 08 pump

    any suggestions on prop size to go with. putting in a 1390 single pipe on my bus with a 08 pump assy. its coming with the oem 14/20 but i was thinking with the big bore we might try to tweak that number. gonna run 93 premix thru blackjack 48's and free flow exhaust. also should i open up the d-plate any more?
    thanks
    dan


  2. #2

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    I would start with a 14/20 Dynafly and you can pitch it up a bit later if it needs it. You will not need or be able to use as steep a prop as a GPR for obvious reasons. Most open up the d plate .1" or .2" on a 1390, depending on what brand/size d-plate. Don't forget the XLT is more limited on air inlets than a GPR, I added an extra 3" vent like the original between the seats, but on the other side, and drilled some holes in the area above the front seat mounts under the steering. Figured it would be hard to get water instrusion there, unless rolled over. My XLT used to suck the seat cover in when the throttle was winged on the trailer. (my seat cover was not glued down from the factory, long story)

  3. #3
    Yellow93's Avatar
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    I ran a 15/25 Dynafly on my ported 1390 XLT.

  4. #4

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    Good point on the air inlet. Never thought about that.. easy mod too. What's the differences between a dynafly 14/20 and the oem 14/20?

  5. #5

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    Nite and day.

  6. #6
    What's the differences between a dynafly 14/20 and the oem 14/20?


    Not trued or ballanced...........

  7. #7

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    OEM doesn't have curved blades on the front edges, or decent performance, holeshot, less cavitation, or better overall performance(does anybody that has modded their GPR use the stock impeller? That says something). However it is your choice.
    Food for thought: Its like tires for your car, 245/50/16 may be the size, would you like Michelin or Goodyear on your sports car or wifes kiddy transport, or do you want chinese knockoff cheap ebay tires that hydroplane when it dews real hard? Both are the same size, but size itself is not the defining factor. in tires, or props.

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