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Thread: what are the advantages of using longer rods

  1. #1
    Senior Member DYNO TECH
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    what are the advantages of using longer rods

    I seem to think the longer rods provide more power on the top with a lower piston speed and longer dwell at TDC.

  2. #2
    Senior Member DYNO OPERATOR
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    something about leverage angle on the crankshaft ops: :? :? :?
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  3. #3
    Senior Member DYNO OPERATOR
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    Yes, you are correct, the piston spends more time at top and bottom dead center meaning the dwell time is longer at top dead center the longer the rod. This allows more time for your fuel to be burned and push the piston down. This is the greatest advantage of rod length. The piston speed will be faster than a shorter rod between 15 degrees after TDC to 15 deg BBDC and so on.
    Bruce

  4. #4
    Senior Member EXPERT BUILDER
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    However... piston compression height LESS than 1.5 is not neccesarily a good thing...

    http://victorylibrary.com/mopar/rod-tech-c.htm
    I'm not hatin... I'm just sayin...

  5. #5
    Senior Member RACING JUNKIE TheYellaBrick's Avatar
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    Great article and source for other info !! Thanks !
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  6. #6
    Senior Member EXPERT BUILDER
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    for a coin it has two sides,some think pick a piston for the application,pick a crank then where ever the rod ends up that it is least important,,,,

    i perfer to keep its value important so my opinion is the three parts must be all considered in the rpm and environment involved-whether n,a, or a power adder

  7. #7
    Not as technical as DRTRCR22 's link but it sounds good

    http://www.iskycams.com/techtips.php#2005

  8. #8
    Senior Member RACING JUNKIE
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    I swapped to a longer rod this past winter in my bbc from 6.385 to 6.535 if there is a difference on the track I've yet to see it ... and yes I'v adjusted looking for it
    David Lanning
    IHRA NHRA 387B

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  9. #9
    Senior Member SENIOR BUILDER
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    does it not have less side drag on the cylinder wall, creating more power too
    ?
    if something goes wrong there is always the cooler!!!

  10. #10
    Senior Member EXPERT BUILDER
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    That's debateable... the theory is less sidewall pressure, but for every change there compensation somewhere else...?

    A prominent local engine machinist/builder believes long rods are good for circle track engines for bottom end torque...?

    Drag race engines...? well, long rods usually have to be used to make up big bore long stroke combinations of big stroker engines.
    I'm not hatin... I'm just sayin...


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