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-   -   Q40 Piston height (http://www.rcuniverse.com/forum/q-40-racing-155/11131400-q40-piston-height.html)

ecoliburger 06-25-2012 11:56 AM

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.

daven 06-26-2012 04:13 AM

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...

ecoliburger 06-26-2012 11:52 AM

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.

Randy Etken 06-26-2012 01:34 PM

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:D

fizzwater2 06-26-2012 01:59 PM

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... :)

Randy Smith 06-28-2012 10:03 AM

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

ecoliburger 07-02-2012 07:52 PM

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?

daven 07-03-2012 06:40 AM

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.

ecoliburger 07-03-2012 11:34 AM

RE: Q40 Piston height
Great, thanks again.

airraptor 07-07-2012 08:05 AM

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.

ecoliburger 07-07-2012 08:58 PM

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.

airraptor 07-09-2012 04:33 PM

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.

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