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F20A Inside F22A4?

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    #16
    Originally posted by mndude07 View Post
    F20a rods aren't shorter...they are longer. Deck height is the same between engines and the f20a has a shorter stroke. You have to make that up with a longer rod. This engine has a 1.65:1 rod/stroke ratio.
    If your referring to my comment from last year:
    F20A rods ARE shorter - Depending on which F20A series you are talking about.

    F20Ax Soch has shorter rods than the F22Ax.
    The F20Ax also has a different crank to the F22Ax.


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      #17
      Originally posted by evil_demon_01 View Post
      If your referring to my comment from last year:
      F20A rods ARE shorter - Depending on which F20A series you are talking about.

      F20Ax Soch has shorter rods than the F22Ax.
      The F20Ax also has a different crank to the F22Ax.
      f20a sohc has 145mm rods, and f22a has 141.5mm rods. Aren't the deck heights the same?...and even the block casting for that matter? If the bore is the same as the F22ax at 85mm, and the stroke is shorter...then you are telling me the rods are shorter...that means the piston must be significantly taller.

      If they are shorter, then what is the rod length and stroke of the engine you are talking about? The F20A sohc I know has a 88mm stroke, 145mm rods, and 85mm bore.
      There are no black and white suspension answers!!!!!!!!!!!

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        #18
        I attached an f20 rod/piston to an f22 crank and found it goes pretty far out the block.
        But I never compared them side to side.
        Also the f22 pistons sat inside the bore while the f20 assembly sits above the deck about a pennys thickness

        Given the shorter stroke, id say the f20 has longer rods anyway...
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          #19
          Originally posted by CB7Man View Post
          I attached an f20 rod/piston to an f22 crank and found it goes pretty far out the block.
          But I never compared them side to side.
          Also the f22 pistons sat inside the bore while the f20 assembly sits above the deck about a pennys thickness

          Given the shorter stroke, id say the f20 has longer rods anyway...
          Exactly. I don't know if people think rod length has to do with stroke or what is going on.

          F22 rotating assembly height at tdc: 95mm stroke/2 = 47.5, 47.5 + 141.5 (rod length) = 189mm

          F20 rotating assembly height at tdc: 88mm stroke/2 = 44, 44 + 145 (rod length) = 189mm

          Both are the same, and the deck height of both blocks is the same. This means the difference is in the piston. I believe the f20a has a 31mm compression height like the f20b, while the f22 has a comp. height of 30.55mm, and when you convert to inches, that rounds to the 0.02 difference you have. Plus, the dome cc's of the pistons are different.

          Based purely on geometry, the F20a has a rod/stroke ratio of 1.65:1. That is better than the H22, or even the ITR's B18C, which revs quite high. A well built F20a should be very happy at 9k revs.
          There are no black and white suspension answers!!!!!!!!!!!

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