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270 Stroker vs Big Bore

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  • 270 Stroker vs Big Bore

    I am rebuilding the engine that I acquired with my car. It is a 68.5mm bore with stock 72mm stroke. I'm rebuilding the bottom end due to a cracked case and was planing on using a OE honda crank. Once this engine is back together I will be starting on a backup engine. What is the benefit to running a stroker as opposed to a big bore setup like mine. I'm assuming the billet cranks are lighter and stronger than the OE honda.

  • #2
    The short version is, that a stroke increase offers the opportunity for increased port/time area values without increasing duration. When an engine is bored, the physical geometry of the port doesn't change much. However, when an engine is stroked, the port can become physically bigger without needing to be raised (since the piston now travels lower in the bore. Therefore, in theory, longer strokes will result in more peak torque. However, theory and practice don't always align and there are piston speed and other considerations with strokers. Generally speaking, most micro folks will favor the 68x74 or 66.4x76 combo's over the 68.5x72 setup. The stock stroke motors tend to make great peak power, but give up a little bottom end compared to the strokers, but anything can and has won races.


    • #3
      Makes sense. I will look into a stroker 66.4x76 setup for my backup engine. That should give me room in the future to go to a 68x74 if I score a cylinder wall. Thanks