Off The Shelf (OTS) Custom ModMotor Pistons - Page 12

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  1. #166

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    What specs did you request on your pistons Eric.


    Ed

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  3. #167
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    .170" skirts, ~1.22" CD, and .010" oversize with a .005" ptw. I wanted to get a little bit of a pin offset but completely spaced on that when talking to Rob. Didn't remember until they were already into production.

  4. #168

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    The CD is why your valve reliefs look different Eric.

    When you move the piston crown up (increased CD), the cut in the top of the piston needs to be deeper to provide the same PTV clearance. The other changes that occur are a little more excess aluminum in the crown underside because of the geometry differences and need to provide support below the valve reliefs accompanied by a slight increase in skirt wear and loading because of the increased leverage the combustion gases have to load skirts with higher (larger) CDs.

    I generally allow Gibtec to specify the PTW clearance based on the piston section thicknesses, skirt type and cam they used in the piston design. There is nothing wrong with using a different spec if you feel you want to optimize a particular piston behavior / performance attribute you experienced with an earlier set of the pistons. I would not expect the 0.005" PTW figure to hurt the piston or its performance / life but it may make them a bit noisy when cold.

    The 0.170" skirts will give up a little skirt integrity but depending on how you load the engine it may not be a significant consideration.


    Ed


    p.s. Almost forgot, the on center pins will, in my opinion, work to your advantage. I believe you will be quite pleasantly surprised with how satisfied you are with that design parameter.
    Last edited by eschaider; 06-10-2016 at 10:55 AM. Reason: Added postscript

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  6. #169
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    Yeah I think these specs will be just fine. I was actually tempted to go down to a .150 or .160" skirt based on the fact that so many people make 900+ with diamond and CP pistons. Which both have considerably thinner skirts.

    I figured .170" would give it some extra headroom but still be a good compromise with regards to weight.

  7. #170

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    The nice thing about Gibtecs is anything you desire in a piston is possible. You are not limited to the custom piece Nick & I designed. You can literally do anything you wish because you are only limited by your own imagination.


    Ed

  8. #171
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    Quote Originally Posted by eschaider View Post
    The nice thing about Gibtecs is anything you desire in a piston is possible. You are not limited to the custom piece Nick & I designed. You can literally do anything you wish because you are only limited by your own imagination.

    Ed
    Yep it's pretty awesome. The turn around time and price is impressive for a custom all billet piece.

  9. #172

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    Quote Originally Posted by Juiced46 View Post
    My Gibtecs showed up last week as well. Very very nice pieces. Thanks again Ed! I dropped them off at my machine shop this week. So hopefully I can start assembling this thing soon. I will be starting a new build thread soon hopefully.
    Looks like you have granite countertops in your garage sorry I couldnt resist

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