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  1. #1

    Prop Pitch For Gp1390r W Triples??

    I am in the process of turning my gpr into a big bore. 1390cc with factory pipes, novi , race fuel, old style pump. i was thinking of starting with a 15/22 for a baseline, what do you guys think?? Thanks Sam


  2. #2
    Duke's Avatar
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    Might want to ask your portsmith what the target rpm is for this motor. I am sure alot of the guys here would be able to help you out if that info was available. Also you might want to consider moving up to the HO pump with those tripples.

  3. #3
    I would like to turn 7900-8000 rpm. I would like to get the ho pump but I have several concord props laying around and would like to use what ive got. But one day i will get the ho pump. thanks sam

  4. #4

    1390

    I searched until I found this topic. I was going to start a new thread but I was sure one already existed.

    I have a Lowell 1390 Triple with HO pump, Advent, and V forces. I am currently running a 15/25 Dynafly but cant spin it enough in the hot temps... 105 here...

    I am still on the rich side and will make up for that but Im curious as to what people are using for prop pitches....

    One more thing, stock carbs....

  5. #5
    mtrager's Avatar
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    Outlaw,

    I have a 1300 and run a 14/22 in the summer.7700 to 7800 rpms. In winter
    that spins 8000 to 8100. Then I go to a 23.

    I have to go to a 14/20 in heat to run between 7900 and 8000. Or a 17/22
    scat swirl.

  6. #6
    philip_gpr's Avatar
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    "I am currently running a 15/25 Dynafly "

    what are your RPMs

    what nozzle are you using (85 or 87)

    who pitched your 15/25

  7. #7
    Quote Originally Posted by philip_gpr View Post
    "I am currently running a 15/25 Dynafly "

    what are your RPMs

    what nozzle are you using (85 or 87)

    who pitched your 15/25
    7400 right now with 1200 grate on the seat with 87 nozzle and its a Fercho bent prop....

    I have a 15/23 that gives me about 100 more revs but it is consistently a mile per hour slower....

    But it is 105 degrees here right now....40 percent humidity

  8. #8
    philip_gpr's Avatar
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    looks like you could try a box stock 14/20

  9. #9
    I have a concord 14/20 in good shape. How much difference in revs would the concord be than the DF???? Im not sure if the concord will work in the HO pump but if not I might just try it in the old pump....

  10. #10
    philip_gpr's Avatar
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    I'd try the concord in the HO pump

    HO pump works better with any impeller than the old pump

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