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Thread: 1300 Bb Rpm's

  1. #1
    Robsauto2's Avatar
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    1300 BB Rpm's

    I think my rpms are too low. 1300 ported BB turning a 14/24 dyna, 6950-7000 rpms at 74 mph.

    Would I see a speed increase with a lower pitch and more rpms?


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    Happily Self-Employed WFO's Avatar
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    Quote Originally Posted by Robsauto2
    I think my rpms are too low. 1300 ported BB turning a 14/24 dyna, 6950-7000 rpms at 74 mph.

    Would I see a speed increase with a lower pitch and more rpms?
    I am no carb guy, but most are seeing peak power 7150-7180. Can you find more power/rpms with the motor? What size nozzle?

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    need4pwr's Avatar
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    Quote Originally Posted by Robsauto2
    I think my rpms are too low. 1300 ported BB turning a 14/24 dyna, 6950-7000 rpms at 74 mph.

    Would I see a speed increase with a lower pitch and more rpms?
    YES. Bring down and your RPMS and speed will increase, your below your power ban.

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    Moderator RX951's Avatar
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    Lightbulb

    A reduction in trailing edge pitch of 1 degree will bring those RPM's up about 80 rpms. You need to be in the 7150 range +/- 50

    Do you have am impeller pitch gauge to check the pitch? You can download one on this site and print on clear trasnparency to check pitch.

    Tommy Jordan (2fast4u) sells the hard clear ones and Randy at WATCON does too.

    And as WFO said, what reduction nozzle are you running ?

    Do you have VF3 reeds? those are good for about 80-100 rpms on a big bore. 100-120 rpms on a 1200.

    Filling in the bilge siphon on the reduction nnozzle will yeild about 50 rpms also. Fill in that visibility spout too.

    Do you have flame arrestor covers (socks) ? if so, make sure they are clean and free of any oil grime that can hamper air flow if you run them.

  5. #5
    Robsauto2's Avatar
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    I have a watcon pitch gauge.

    85 mm nozzle

    vf3 reeds

    no covers on the pro-tec arrestors

    I will give a list of mods soon

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    Happily Self-Employed WFO's Avatar
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    If you have an 87mm laying around, try it out. Should pick up 80 or so rpms.

  7. #7
    Robsauto2's Avatar
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    Quote Originally Posted by RX951
    A reduction in trailing edge pitch of 1 degree will bring those RPM's up about 80 rpms. You need to be in the 7150 range +/- 50

    Do you have am impeller pitch gauge to check the pitch? You can download one on this site and print on clear trasnparency to check pitch.

    Tommy Jordan (2fast4u) sells the hard clear ones and Randy at WATCON does too.

    And as WFO said, what reduction nozzle are you running ?

    Do you have VF3 reeds? those are good for about 80-100 rpms on a big bore. 100-120 rpms on a 1200.

    Filling in the bilge siphon on the reduction nnozzle will yeild about 50 rpms also. Fill in that visibility spout too.

    Do you have flame arrestor covers (socks) ? if so, make sure they are clean and free of any oil grime that can hamper air flow if you run them.






    So how far from the trailing edge do you bend the blade? Just the last inch or more?

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    Moderator RX951's Avatar
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    On a dynafly I could not tell you. the geometrical shape is different.

    On a dynafly, I beleive you need to get it properly machined because the O.D. of the impeller changes as you adjust pitch.
    Check fitment of your impeller clearance to liner also after each adjustment on that dynafly.

    You may want to contact an impeller specialist over that one.

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    spud's Avatar
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    Rob, did you get an index wheel and check your new crank? Frank says its important to check them even if they are brand new trued and welded cranks from Riva.

    I bought a brand new flywheel from Riva and sent it to Frank to be lightened and balanced. He told me it was way out of balance. I did notice the flywheel did not have any marks on it from beng balance. For $125 that will be a mod I always perform to any engine I pull to rebuild.

    We need to get a good tuning party going in a couple weeks at Senator's. OCGPR should come we could all make a dayof it.

    If Bill buys Mark's lake boat maybe we could get them out to do the deal.

    Anyways let me know about the crank. I'm getting a degree wheel and I'd like to know where to get one of those trick dial indicators that screws into the spark plug holes.

  10. #10
    Moderator Insanediego Joe's Avatar
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    We all have a date at long beach marine stadium for a race on the 12th and 13th of next month. Mark might and I said might make the trip to san diego before then to do some tuning on his tripple piped ski for the race.

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