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90.70mm vs 95mm vs 97mm Stroke

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    #16
    I definitely would do this crank. It would be even better if a deck plate could be machined to allow you to run some modified H22 rods with it as well. Or try and get some custom 27mm pistons.
    My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

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      #17
      Originally posted by Joey GT-R View Post
      I thought I'd just throw it out there, but the K24A2 crank at 99mm can be machined to fit H22s and F22s. They rev to 8K stock so paired with the right rods and pistons you might can have the longest stroke of all and still rev fairly high. Or if you're just after the most torque possible, any of the other K24s would do. If I was to go back to an F22A build, I would consider this.
      Max rev on a k24 listed is 7600. Its not the crank that allows a high rev its what's attached to it. While the crankshaft does give a certain mean piston speed based on rpms, the hardware attached ultimately decides how far it will go.

      Revving past 25 m/s is just wanting to shorten the engines life.

      Just go here: http://thefirstgensite.com/code/maxrpm.htm

      Always run the longest rod possible, that is as long as it doesn't compromise the integrity of the piston or clearancing the cyln walls. Contacting the piston manufacturer and asking them about wristpin location mods will let you know what you can do.

      Offsetting the wristpin by 1 or 2 mm(closer to the intake valves I believe) can gain power, as it allows for a slightly longer push on the crankshaft

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        #18
        what about using the f23 crank and having it knife edged to reduce drag? Acceleration would improve but im not sure if it would yield big hp gains.

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          #19
          Knife-edging crankshafts is an expensive process that's not proven to have worthwhile gains. What you may gain in acceleration without a load, you are likely giving up in longevity. Far too many people think that the crankshaft is submurged in oil or something.

          Also, the F23A is a decent crankshaft but the smaller rod journals mean that there are better options.
          My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!

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            #20
            I wouldnt put too much thought into rs ratio unless you are wrapping it out all day everyday. I ran a 1.4x for a couple years revving to 8500 damn near everyday for 35000 miles til it finally spun a rod bearing due to my bearing clearances being too tight.

            You can play the math game all you want but in the end it doesnt have all that much effect. You arent building a f1 motor
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              #21
              Originally posted by ferenza View Post
              what about using the f23 crank and having it knife edged to reduce drag? Acceleration would improve but im not sure if it would yield big hp gains.
              Only useful when a good machineshop can balance the rotating assembly. You don't want to upset the counterweights. Yes it reduces windage but your biggest hp gains on weight are at the rims and tires for rotational weight, and better yet reciprocating weight being reduced makes huge gains.

              A heavier crank makes smoother power curves, and probably reduces wear on the journals significantly over a lightened one.


              Id get it balanced that's it.

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                #22
                Originally posted by Joey GT-R View Post
                I thought I'd just throw it out there, but the K24A2 crank at 99mm can be machined to fit H22s and F22s. They rev to 8K stock so paired with the right rods and pistons you might can have the longest stroke of all and still rev fairly high. Or if you're just after the most torque possible, any of the other K24s would do. If I was to go back to an F22A build, I would consider this.
                Yeah but how much taller is the k24 deck than the f/h
                Some know me as the "Tranny Guy"

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