Thread: Fast Fred's OMC Mod 50 secrets Thread #2

  1. #131
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    hay sheuninck,
    i don't have one of them, i do have 3, 1 1/2" 3jet carbs, they are a set. i may or may not have the jets for them, eather way hows 75bucks sound, you pay your shippin. i'm makin it shippin week, be firin stuff outa hear, lets me know if ya needs them

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  2. #132
    Team Member sheuninck's Avatar
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    Default carbs

    Fred,
    What is the difference in these carbs, vs the sst60 carbs as far as performance goes?

  3. #133
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    the 3jet carbs have an intermeadiat jet to help the moda move from lo speed to high speed. is it better than the SST carb, ? , thay should work just as good or better. late model Stingers had 3jet carbs on them from the factory, if you have an old style Stinger powerhead, (came with the smaller carbs) these would be an upgrade, you would go faster.

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  4. #134
    Team Member sheuninck's Avatar
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    Default ok

    fred. i sent you a pm

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    When you drop the Mod 50 pistons and the long rods in a 49er without altering the port timing how does it perform re the short rod motor?

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    Default L O N G vs short

    From the center of the rod(crank end) to the top of the piston port timing is the same on both short and long. As for ferformance:
    shorter rods are faster on punch------- with a lot of piston/motor failure
    longer rods are faster on top--------not much if any piston/motor failure

    Reason; Shorter pistons have windows(ports) and are close to wrist pin.
    Longer piston set-ups have no holes(unless added for finger and
    boost ports)

    HOW MANY HAVE YOU TORE UP????????? Phil

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    What I was getting at is the port timing is different not just the rod angle which helps the low/high torque with short/long rod issue as per any engine.

    X amount more of crank rotation in the long rod engine will be required to uncover a port versus the short rod motor which sounds counter to the torque effect of the short/long rod motor story.
    ( you would need to lift the ports on the long rod motor to make the timing the same as the short rod motor)

    http://www.torqsoft.net/piston-position.html

    Has anyone ever measured the timing?

    I have pulled many std pistons which have cracked so close to failure...they did always look ugly, i'm all for the long rod version with the raised pin.

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    hey Phil McDaniel, made some room for ya in my PM box, that should go out today. think it's time for some more shots of Moda parts over hear.

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  9. #139
    Team Member Bill Gohr's Avatar
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    Default Long rod

    Quote Originally Posted by Phil McDaniel View Post
    From the center of the rod(crank end) to the top of the piston port timing is the same on both short and long. As for ferformance:
    shorter rods are faster on punch------- with a lot of piston/motor failure
    longer rods are faster on top--------not much if any piston/motor failure

    Reason; Shorter pistons have windows(ports) and are close to wrist pin.
    Longer piston set-ups have no holes(unless added for finger and
    boost ports)

    HOW MANY HAVE YOU TORE UP????????? Phil
    Pistons will last longer also because of less piston rock near tdc.

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    Default Piston-rod durability?

    With respect to wrist pin location, please study engines other than the Mod-50. For a quick comparative study, go to the Wiseco catalog. You'll see something close to a 50/50 position quite common. SAE papers also confirm ring package stability (sealability) and piston/sleeve life are actually extended nearing a 50/50 position with respect to skirt length.

    In the end, none of my FE engines ever mechanically failed a rod/piston, short or long. They all suffered thermo-dynamic failures, primarily due to a lean mixture condition (fuel starvation from one of several causes), and secondly due to excessive spark advance.

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