Nova .28

Discussion in 'Motors Forum' started by David Ashcroft, Jan 25, 2020.

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  1. Jan 25, 2020 #1

    David Ashcroft

    David Ashcroft

    David Ashcroft

    Well-Known Member

    Joined:
    Jan 26, 2014
    Messages:
    1,208
    I measured my Mod Nova 28 on the metric engine programme ,and got 185exh
    Rotor opens 219 ATDC and Rotor closes at 65 with a totel open duration of 206.
    The blowdown is 31.7 as expected because this engine was modded to rev.

    What surprised me though was the button CC volume of 0.37cc !! with the plug in,,which will end up with a trapped CR of 7.6 that's without a any shims and .0.16" clearance ,I not sure why the button was enlarged so much,,although this is a converted car engine to run low 25% nitro
    .

    I am thinking a new button made to 0.26cc for high nitro and set clearance to 0.008" for a trapped CR of 10.5 .which will give the engine more torque to pull the prop better.
     
    Last edited: Jan 26, 2020
  2. Feb 13, 2020 #2

    Gary Lauer

    Gary Lauer

    Gary Lauer

    Active Member

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    Mar 21, 2019
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    Location:
    highland Mi
    I also have a 28 marine and without any shims have .012 clearance. How do you make that smaller? sand the top of the cylinder?
     
  3. Feb 13, 2020 #3

    David Ashcroft

    David Ashcroft

    David Ashcroft

    Well-Known Member

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    Don't Sand the cylinder..
     
  4. Feb 13, 2020 #4

    David Ashcroft

    David Ashcroft

    David Ashcroft

    Well-Known Member

    Joined:
    Jan 26, 2014
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    I am currently having a new Head Button machined now with a smaller bowl cc..
     

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