We received this commentary from a Planethobby / Novarossi field rep that test engines for us.  He received the Novarossi R46 Pylon Engine configured with the 10mm carb.  Below are his notes for your assistance in configuring and designing a power plant for today's .40 size airplanes. 

This engine is the pinnacle of design in Italian racing engines.  Small features such as induced turbulence by flow grinding the crankshaft, port magic (9 ports) for improved clearing exhaust and silicon inserts in the crank to reduce weight for improved acceleration out of those pylon turns make this engine a "best of class".

From our Field Rep

I wanted to know how this engine would work on a 40 size sport pattern plane using the most common 40 size props, as opposed to the smaller pylon props for which it is intended.  I used the R46 Pylon version with the 10mm carb.  After seven length changes on the header, I got it up to 17,400 RPMs with an APC 10X6.  I was more than a little impressed. Without changing exhaust length I tested an APC 9X7 and got 18,300  RPMs  ...and with an APC 11X6, 15,950 RPMs.  If I had 'tuned' for either of these props, I'm sure there would have been more available.  The final length from where the header butts to the engine, to the beginning of the maximum pipe diameter is exactly 11".  For accuracy, I measured using a fabric tape measure like a seamstress would use, in order to follow the curve of the header.  Conclusion...  In addition to the power, it is a very sweet running engine in general, with a very nice, stable idle.  If you buy one of these, you will be buying an extremely powerful, and versatile engine of the absolute highest quality.  Over 35 years in the hobby, and always with my ear to the engines.  The R46 Pylon  is by far the most impressive engine I have ever run.

Honestly, I may still have left a few rpms on the table.  Where I stopped would already be way in excess of what is needed for my UltraSport Hybrid pattern plane.  However, when I finish the plane, I will start with the header 1/2" longer than it is now, and tune for the bigger prop. (Intend using an 11X6) I am sure that I will end well above 16K, even on the 11X6.  As an example...  16,000 rpms  X 1.15 unload factor = 18,400 rpms X 6 = 110.4 mph prop speed divided by a factor of 1.056 = 104.5 mph theoretical top speed   ...minus 15% (estimated) for air frame aerodynamic inefficiency = 88.9 mph.  That's estimated level flight speed at 16K rpms.   Faster than the plane can go probably (It will be over 16K)  ...and if I ran a 10X6?  Yikes!!  I'm willing to bet that I will find myself throttling back a fair amount.  ...even on vertical.  Thanks again for indulging my engine obsession.