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Thread: ROD LENGTH BBC

  1. #1
    Junior Member SHOW GUEST
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    ROD LENGTH BBC

    i am building a 13.5-14.5 compression. 525 bbc engine. i have 427 tall deck block and 4.375 stroke crank. any suggestions on the longest rod legnth i can use for max hp and torque for drag racing?.i am considering 6.7 or 6.8 rod length.i will ocasionally spray up to a 400hp shot of nitrous as well.thanks

  2. #2
    Senior Member RACING JUNKIE jmarksdragster's Avatar
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    Get the piston/pin height/ring package that will work the best and connect it. Don't worry about rod length.
    Mark Whitener
    http://racingfuelsystems.myfunforum.org
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    Good work isn't cheap, and cheap work can't be good.

  3. #3
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    ROD LENGTH BBC

    ok,kind of a broad answer though!!

  4. #4
    Senior Member RACING JUNKIE jmarksdragster's Avatar
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    My point was I wouldn't worry about the rod length, order the pistons for your combo without running the pin into the rings if possible. Either a 6.7 or 6.8 should work OK, a 6.8 will give you a 1.2125 pin height, 6.7 is 1.3125. By comparison, I have a 447 SB2 with a 4.125 stroke, 9.320 deck, 6.125 rod and roughly 1.13 pin height. I am building a 460 SB2 with a 4.25 stroke, 9.5 deck, 6.2 rods, and depending on final deck height, around 1.18 on the pin height. Give the piston company you chose all your final specs and they will tell you which will be the most stable piston, and get the corresponding rod.
    Mark Whitener
    http://racingfuelsystems.myfunforum.org
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    Good work isn't cheap, and cheap work can't be good.

  5. #5
    Senior Member EXPERT BUILDER
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    i have heard that nitrous pistons need to really have a minimum of 1.25 pin height to live.may be a wives tale but again piston manufacturer will be able to help you out the most.also stick with 2618 grade aluminum forge piston.no cheapie srp or mahle piston with the kinda nitrous your talking about.ross je aries diamond are some of the best

    half of stroke is 2.1875.
    good minimum piston pin height 1.25.
    deck height is 10.2 *about*.


    so subtract half of stroke and minimum piston height and that is ball park rod you will have.so my math says 6.7625 which will should work out with a 6.7 inch rod.but check with manufacturer like mark said try to keep piston pin out of the ring grooves...good luck

  6. #6
    Senior Member RACING JUNKIE
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    If you plan to run that much nitrous, i would suggest you invest in a blower/nitrous piston, meaning that the top ring is 7/16" below the deck of the piston and like mentioned above buy only a 2618 grade alum. piston, rod length is not that critical IMO.

    Zip.

  7. #7
    Junior Member SHOW GUEST
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    BBC ROD LENGTH

    FIRST, I WOULD LIKE TO THANK YOU FOR YOUR INTRESTS AND REPLIES. NOW! SO FAR I WILL GEAR TOWARDS 6.7 MAYBE 6.8 ROD LEGNTH. THIS 2618 GRADE ALUMINUM SUGGESTED-WHO FOR MANUFACTURER? ALSO GAS PORTED PISTONS OR NOT WITH 400HP SHOT OCCASIONALLY!THANKS

  8. #8
    Senior Member RACING JUNKIE
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    If your going to run more than a 300hp nitrous setup, I'd suggest a good vacuum pump.
    If your on a budget and don't wont to buy nitrous pistons and vacuum pump. Run a 250hp setup you wont notice a ton of difference, but sure is easier on parts. Expecially those bought on a budget. Its all about combinations.


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