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  1. #1

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    Q40 Piston height

    Can someone explain or provide a link to a description to setting up a Nelson Q40 engine? Dont really understand setting the purpose or method of setting the piston clearance and or liner height.
    Is it just a matter of fiddling around with shims until the engine is running the best it can?
    Thanks in advance.

  2. #2

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    RE: Q40 Piston height

    Does it run ok? Its most likely correct if it is. I would only mess with it if it was running poorly. Its a tricky subject unless you have the right tools, is there anyone in your area that races that could show you? There is a lot of nelson guys in CA, but I understand it is a big state...
    Dave Norman
    29w

  3. #3

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    RE: Q40 Piston height

    Not running at all, its in parts which is the way I got it. I have all the tools needed, figured if I got a basic idea of where to start I can figure it out.
    Thanks,

  4. #4
    Randy Etken's Avatar
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    RE: Q40 Piston height

    Go to DarrolCady.com
    Click RC Accessories
    Click racing tools
    Super Accurate digital racing engine measuring tool, Click how it use or click on teamseaholm.
    You should get an idea of what you want.
    Get you plane from Q500racing.com
    Randy E.
    www.Q500Racing.com

  5. #5

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    RE: Q40 Piston height

    Randy, why would he want to get a Q500 plane to put a Q40 engine in?

    Just pulling your leg a little...

    No matter where you go, there you are!

  6. #6

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    RE: Q40 Piston height

    Are we talking Nelson short stroke or long stroke here?

    Here are my setup numbers for my long strokes. Keep in mind I am in Calgary at 3300 feet ASL.
    Individual results may vary. You will need to play with the setup +/- .002" or so.

    Sleeve height = 0.192" at TDC
    Head clearance = 0.019" to 0.022" @ TDC (depends on glow plug longevity, piping characteristics)

    For short stroke, it's been a long time but if memory serves me it might be something like:

    Sleeve = 0.196" and Head = 0.013" - 0.015"


    It takes a bit of playing around but if you have no where to begin, start with these numbers.


    Randy Smith

  7. #7

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    RE: Q40 Piston height

    Its a short stroke and thanks for all the suggestions.

    So Randy if I set it up to your numbers then run the thing, if it wont needle well then probably too much compression?

    Is the idea to creep up on the compression until you get peak rpm?

  8. #8

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    RE: Q40 Piston height

    I ran most of my SS heads at .016 on Q40 motors, not quite as tight as Randy. Also, don't get hung up on ground RPM numbers. Start at .015- .016, and fly it (if you can use a gun, or other speed measuring device) and find out where you are. Then lower it a bit and do it again and compare. You may get higher ground RPM with the tighter head, but that doesn't mean you will go any faster. These motors unload more than your standard sport motor, and leaving the head a little higher with a slightly smaller pitch prop and your unload could easily wipe out any gain from a higher pitch prop with a tighter head.
    Dave Norman
    29w

  9. #9

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    RE: Q40 Piston height

    Great, thanks again.

  10. #10

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    RE: Q40 Piston height

    lance you working on getting a plane for the woodland race? I have nelson FAI engine and plane. maybe could get them going and fly them out at the field? i know Pat and Chuck have ran those before and could help. I know Robert at APC would help also.
    AMA # 126183
    Fly light, fly fast and fly low.

  11. #11

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    RE: Q40 Piston height

    Yes, got a q500 that I've been flying with a nelson and just got a Jet engine for the 426 class. Got a Miss Candace that I have flown a few times but removed the engine, trying to get it going again for the Woodland race. Flown with Pat and Robert but dont think I have met Chuck.

  12. #12

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    RE: Q40 Piston height

    when you go fly those let me know i would like to fly one of those someday and i can watch you and or help.
    AMA # 126183
    Fly light, fly fast and fly low.


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