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long VS short rods

Discussion in 'Engine Building' started by ek9r, Sep 25, 2003.

  1. ek9r

    ek9r Senior Member

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    i was wondering about how long, or short my rods should be while running 12.5:1 pistons in a b18c5 using jun 3 cams. I was reading an article from turbo mag online, they say-
    longer rods= slower reving engine w/ long duration cams
    shorter rods= higher reving engine w/ shorter duration cams

    now they got me thinkin that if i am running the long duration of the jun 3 cams, that i would want to go with a longer rod setup. Is this even possible to do considering piston to valve clearance? Hope someone can give me some advice.
    thanks in advance!
     
  2. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Longer rods = more dwell time and more progressive piston acceleration in and out of TDC and BDC, not slower revving... but the cam recommendation is correct. Just run your stock rod length setup- if you don't, you start getting into custom rods and totally custom pistons. I do like my long rod setup though!

    :lol:

    You can go with longer rods if you move the wrist pins up in your pistons, and that wouldn't affect your valve to piston clearance. On the other hand, lots of people have excellent results with Jun 3 cams on stock stroke geometry setups.
     
  3. ek9r

    ek9r Senior Member

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    i really feel that if i optimize that "longer dwell time" (allowing more air and fuel to enter the combustion chamber) that i would see better results and pull out max potential of the long duration of the jun 3 cams. What do you suggest i do. How do i know how long of a rod to go with, if i move the pin up higher in the pistons? will i have to modify the block at all due to the increased angle of the longer rods?
    thanks John
     
  4. JDMilan

    JDMilan Senior Member

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    if your trying to bust low low et's going NA then you might consider the minimal gains. I say stick with your current rod length, upgrade to a good aftermarket unit, if you are rebuilding, custom rods, cranks, pistons are for the big boys with lots of cashish from sponsors..
     
  5. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Your rod angle actually goes down, not up if you get longer rods- so you don't have to modify your block unless you make the rods MUCH longer than your stock ones.
     
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