Q40 Nelson Setup - Sleeve Height and Head Spacing

This article is intended to document my experiences setting up a Nelson Q40 engine. At this point in my rejuvenated racing career I've flown my Vendetta 2 times, so I'm by no means the world's foremost expert on this subject. I have however been picking the brains of a lot very seasoned racers. This information is my take on the suggestions given to me by Larson, Bridge, Norman and others.

I use the dial caliper and depth mic combo from Darrol Cady. This is a very nice digital read out tool that I've found to be of good quality and very handy for other projects as well. Darrol does a good job of explaining how to use this tool and the accompanying sleeve spacer ring. I won't spend much time rehashing the measurement process, Darrol explains it very well here:

http://www.darrolcady.com/Accessories/LinerTool/newlinertool.html

I will describe a few things not mentioned there and some other tricks I've picked up along the way.

Keeping Track of Engine Set-up

Currently I own 2 Q40 engines, so the following may not seem that important. Like all racers, I hope to continue to expand my engine inventory and found this is a good method to keep track of these shiny engineering marvels. While I was flying combat I had as many as 6 Irvines. This identification method allowed me to track each engine's life and performance as well as where it was set-up.

I use steel marking stamps that can be purchased from www.mcmaster.com on page 1760 of the online catalog. I use the 1/4" height set. It is best to remove the head before marking the engine lug. I wrap my fingers around the stamp to protect the engine. I'm not that good with a claw hammer and figure fingers will heal, engine cases won't.

Establish Engine Baseline

Like I mentioned earlier, I won't go deep on the measurement process. I measure everything with the shims removed from both the head and the sleeve. This establishes the motor baseline or the tolerances of the motor. In my mind, it will be easy to measure and add shims at the field. Measuring the motor may be more cumbersome. I document everything in a note book I carry in my flight box. So, when it is time to make adjustments I'll have a quick reference and won't have to remeasure or rely on memory.

Shim Engine to Desired Timing

This is one of those subjects that if you ask 10 people, you'll likely get 10 different answers. Along with 10 different reasons why those numbers are correct. I don't have enough experience to say which I prefer but do see the value in a couple theories. Norman told me he breaks his Q40 motors in a little high on the sleeve height. This makes excellent sense in my mind as it reduces compression and pinch slightly which will put less stress on the rod during the initial break in. Plus, the new motor I got from Bridge was also set up a little "high". "High" of course being the relative term of much debate.

I set this motor up at .197" for the Sleeve Height and .016" for the Head Spacing. It is common practice to refer to this setup as 197/16, meaning 197 and 16 thousandths of an inch. The following illustration is how I think of the shimming process. You have to keep in mind that by adding sleeve shims, you also increase the head spacing. Hopefully, this image will make this more clear.

Engine Re-assembly

When you have the sleeve shimmed to your liking, is very important to get the exhaust port lined up with the case when inserting the sleeve. I made a big time rookie mistake with this step on my first new Q500 motor, fortunately it didn't hurt the engine. I won't waste your time explaining the bone head move but will say, a Neslon will run with the sleeve 90 degrees off.

Slide your sleeve back in place and check the exhaust port alignment with the case. There is a mark on the top of sleeve that should point towards the front of the motor. You can use this mark as a reference but not for fine tuning the sleeve orientation. Use the exhaust opening in the case and exhaust port in the sleeve for fine tuning. The sleeve port is slightly smaller then the case opening, center the port in the case opening.

Put the desired shims on the head and slide it back in place. Check the exhaust port alignment again to assure it didn't move while installing the head. If it did move, remove the head and reposition the sleeve. When you're satisfied with alignment insert the head bolts and get each bolt started. Run each bolt down till it just snugs up, only finger tighten at this point. Use a cross tightening pattern to get everything seated. It is very important you DO NOT tighten the head bolts yet. Re-examine the sleeve orientation and make sure the head is seated evenly on the sleeve.

Use a torque wrench and the cross tightening pattern to secure the head. Darrol recommends 11 in-lbs of torque for the head bolts. He also sells a nice torque wrench on his site. I sneak up on the final torque in 3 increments. For example, start at 7 in-lbs, then up to 9 in-lbs, and then finally torque it down to 11 in-lbs. It is important you move across the head, cross tightening pattern, when tightening so you don't warp the head.

Engine Care

Now your new horse is ready for action. Lyle and Randy have both told me about the importance of engine maintenance. Specifically, the removal of carbon build up from the top of the piston and head. This should keep your new stallion in peak condition, just like the driver, right. Lyle recommends a product called Nevr-Dull and Randy likes a product called Blue Magic. My local automotive store had Nevr-Dull so I went with it. This a wadding material that is designed to remove oxidation and shine aluminum, brass, and other metals. It is non-abrasive so you're not removing material just deep cleaning. It works well for shining up Nelson mufflers as well.

Once clean, don't forget to add oil to preserve the bearings and to fight rust. I've been using the Powermaster after run oil from Darrol and really like it (This is starting to sound like a DarrolCady.com advertisment, wonder if he'll give me a discount:-). Norman showed me a cool trick to keep the oil in the motor. Use the expanding ear plugs in the venturi and exhaust. This is a good one that works well on sport planes as well.

Hope this was informative and an enjoyable read.

Have fun, fly hard.

These pictures can also be viewed in the TEAMseaholm Photo Album under the album titled Q40 Nelson Setup.


 
Published: 1.29.2005