Larry Driskill
Posts: 659
Joined: 6/2/2003
From: Lubbock,
TX, USA
Status: offline
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I am pretty sure I have posted this somewhere before, but would have been sometime ago. It is from my "Tips for the VA MKII", but most will apply to the Norvels too.
The abridged version would say: Buy clean fuel -Keep it clean; use enough nitro to help keep the needle setting broad (15-30%); use all castor for the oiling duty (20-22%) or at the very least 1/2 castor; to make their best power, these engines need to wind up tighter than the Coxes - don't over prop; make sure you have a good starting battery that will glow the plug element a bright orange; be really careful using an electric starter or you will break something.
"1/2a flying is great fun. In no other engine class do you stand to get so much airborne time for so few bucks. No other class of gas powered model is as likely to bounce rather than break when the ground smites the aircraft. However, when compared to larger equipment, 1/2a engines and planes are more subject to the whims of the weather and nature and less forgiving of inappropriate technique. Clean fuel, hot starting batteries (with the Nelson plug 1.5 volts is nice), fresh glow plugs, and attention to detail are rewarded.
As with many ABC engines, most VA MKIIs may seem ready to go after only one or two runs. However, do the new engine a favor by putting half a dozen two minute ground runs on the engine before launching off into the clear blue. Needle settings for these runs should be just on the rich side of peak RPM and with a small prop. Avoid sloppy rich runs will not allow the engine to heat up properly and put extra stress on the rod and crank. I use a black Grish 5x3 propeller cut to 4" and fuel with 20% castor oil and 30% nitro for break-in. For better front end lubrication, and easier starting put a drop of light oil just behind the prop drive washer before you start flipping. This is especially important on a new engine and is also a good practice for the first flight of the day even after the engine is broken-in.
Proper head clearance is magic when consistency is the issue. The engine is delivered with .006" to .010" clearance above the piston at TDC. Those numbers have worked well in many situations. However, if you are blowing plugs, the head is probably too close for your fuel / weather condition and an additional head shim may be needed. Start with an additional .002" or .004" shim.
Before installing a new glow plug, smear a small amount of Permatex anti-seize compound (part number - 133a at auto shops) on the plug threads. This will help keep the steel plug from seizing in the aluminum head button. If the plug seizes, the head button will slip and turn under the retaining ring when you attempt to remove the plug. If you can not get the plug out you may have to remove the retaining ring and head button from the engine and hold the button while you remove the plug.
If the engine ever feels as though there is a compression leak, check carefully for leaks around the plug and the head retainer. Light oil or WD-40 will usually bubble if there is a leak. If there is a leak, make sure your plug is a Nelson Standard (no machined cuts on the flats of the hex), or a recently purchased HD, and also tighten the plug. If a black "liquid" shows up in the exhaust oil there is probably a problem. Stop running the engine and investigate. The cause may be a piston that has backed off on the wrist pin carrier.
If you use an electric starter make sure the engine is not flooded or you may bend the rod or break the crank.
Top performance depends on using the proper propeller. When choosing the prop remember that these engines need to turn up higher than older style engine to be in their proper power band. Some 1/2a props of the nylon and plastic cast variety have crooked, out of true hubs. If the spinner / prop bolt is wobbling, true up or discard that prop.
Compared to a .36 or .40, these diminutive fellows use so little fuel that there is little reason to use fuel that may have inadequate or inappropriate oil. Use fuel with 20%, or greater, castor oil. In the VA, castor oil based fuel will make more power and promote durability. The use of fuel with low oil, or only synthetic oil, will most likely result in premature wear of the wrist pin end of the connecting rod. Just because you have had good luck with a particular fuel in your .40 RC engine does not mean that fuel has a appropriate oil content for a plain bearing .049. Keep your fuel clean and tightly capped. I filter mine when I put it in my pitbox fuel can and again as I draw it from the can."
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Larry Driskill
Kitting It Together
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RE: Norvel Engine FAQ - 
