Proper liner/head spacing for Nelson QM40 (Full Version)

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jprge C. -> Proper liner/head spacing for Nelson QM40 (7/5/2006 4:20:21 PM)

Hello,
Thank you for the information with the spinner for the Nelson. Can someone please tell me the correct shim set up for the nelson. I measure the engine with out shims, the head measures .185 and the liner to the top of the piston is .186" The shim under the liner when I got the engine was .010" and under the head was .003" Does this sound like a proper setting. I am using the new lighter pitch CF quarter midget APC prop.

Thanks
Jorge



garys -> RE: Proper liner/head spacing for Nelson QM40 (7/5/2006 5:31:22 PM)

That sounds good to start, each engine has its own characteristics and they don't all run with the same settings. Did you get the engine new from Dave Shadel? If so, why did you bother to take it apart? Dave's already test ran it and has it set properly so there isn't a need to take it apart.



Ed Smith -> RE: Proper liner/head spacing for Nelson QM40 (7/5/2006 10:54:31 PM)

Gary and I will never agree on this. I recommend that a new engine should always be taken apart and washed out. Rarely have I washed out a new engine and NOT found aluminum chips in the bowl.

The measurements quoted will give 0.196 deck height and 0.014 head clearance.

The two Q40s I purchased last year had 0.196 deck height and 0.017 head clearance. Yours may be a little tight.

However, as Gary stated, not all engines run the same. You will have to fly it and try it. Make some changes, it is a learning process.

Ed S



daven -> RE: Proper liner/head spacing for Nelson QM40 (7/5/2006 11:20:16 PM)

I've done it both ways, they all vary a little. I personally like to take them apart and measure myself, but I put trust in Dave on my two engines this year, and both seem to be working well, so what do I know.

I typically run .196 and .016 on Q40 motors, many are running closer to .193/4 and .013/.014.



diggs_74 -> RE: Proper liner/head spacing for Nelson QM40 (7/6/2006 2:48:23 PM)

I always thought that the tighter the head the harder it was to needle... I don't know if that's true across the board but I know it is with one of my quickie motors... It seemed to make it really finicky...



daven -> RE: Proper liner/head spacing for Nelson QM40 (7/6/2006 3:31:55 PM)

a tighter motor will be more finnicky to needle, but can also be faster.

Take your tradeoffs, I prefer an engine that I can consistenly get a good needle.



diggs_74 -> RE: Proper liner/head spacing for Nelson QM40 (7/6/2006 3:41:04 PM)

I don't have a lot of experience with these yet so I prefer to make at easy as possible...



Super Splatter -> RE: Proper liner/head spacing for Nelson QM40 (7/6/2006 4:47:20 PM)


quote:

ORIGINAL: diggs_74

I don't have a lot of experience with these yet so I prefer to make at easy as possible...


aka.... I'm from Wisconsin[:D]



diggs_74 -> RE: Proper liner/head spacing for Nelson QM40 (7/6/2006 5:48:39 PM)

I should have seen that coming... [8|]



daven -> RE: Proper liner/head spacing for Nelson QM40 (7/6/2006 7:17:59 PM)

A beer in one hand, a caliper in the other, you'll figure it out in about 2 hours :)

Then again, who am I to judge :)



diggs_74 -> RE: Proper liner/head spacing for Nelson QM40 (7/6/2006 8:13:44 PM)

Everything goes better with beer [:D]



jprge C. -> RE: Proper liner/head spacing for Nelson QM40 (7/7/2006 2:42:11 AM)

Hello,
I bought the engine and airplane brand new at a swap meet back in late April. I have just had to work so many hours it is only now I am getting to work on it. The engine is brand new, I even have the paperwork and the credit card reciept was along with it. It was bought from Nelson Competition Engines, PA in 2004. The reason I took the engine apart is going by what Terry Prather allways said, "it can't hurt if you are careful and you might find something I missed"
I left the engine alone and ran it with an FAI prop I had that I cut down to 7". After 5 runs like that I put the CF APC prop, the 7.8x8 I believe and it turns 22,800 and will pinch to 23,700. Friday I hope to fly it and will report the results.


Jorge



daven -> RE: Proper liner/head spacing for Nelson QM40 (7/7/2006 2:51:38 AM)

If your getting those kind of rpms, your doing better than me :)



jprge C. -> RE: Proper liner/head spacing for Nelson QM40 (7/21/2006 4:20:49 PM)

Hello,
Well I now have 6 flights on the plane and engine and it really goes quite well. I was hoping to take it to Bowie, but I have found the race has been cnceled. I will have to wait until next year to get a true comparison on how well it does go. The Nelson is very easy to run and the final set up with the shims has ended up at .009 under the liner and .003 under the head. It needles well and runs perfect through the tank.

Jorge



SmokinJoe -> RE: Proper liner/head spacing for Nelson QM40 (8/3/2006 12:46:21 AM)

Deleted.






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