That's the beauty of experimental aviation. We can build a plane to tinker with a one-off engine and "experiment" to see if we can make a ____ engine successfully power the aircraft. Then continue tinkering to improve it as much as one's ability allows. Most people, myself included, want a solid, proven and reliable engine, so stick with Lycoming. That's not to stop one from wondering or trying out a different option.
That's one of my "7 wonders of Van's Aircraft". Van's has been stubbornly loyal to Lycoming with one major exception (RV-12). That has dramatically increased demand for Lycomings and decimated the used engine market. To my feeble brain, I would have thought that more engine options would be beneficial to Van's since engine supply would be more broad and probably cheaper. A larger used engine market to tap into. Cheaper engines means more affordable airplanes and more airframe kits sold.
Continental makes great engines. Some would want a -470 in an RV-10 or the -360 Continental options for the 4/6/7/8/14. The IO-240 might work well in an RV-3 and RV-9. UL would be great to provide support to as well. New offering, but good factory support creates competition amongst engine manufacturers.
But what do I know, haha.
1) I am not against experimentation or tinkering... Heck I experiment with my Scotch and Cigars all the time.
However I am trying to help people. Seriously.
2) People can do as they like, but some people are working on propaganda "Lycoming" or "Continental" are OLD technology, automotive engines are MODERN and implied better. I would dissuade people of that false notion Lycs are inferior or old tech, for aircraft.
3) When you buy a Lycoming or TCM (Continental) you are not just buying an aircraft engine, you are buying processes, best materials, QC, publications, training, continuous improvements from millions of flight hours and most of all an engine SPECIFICLLY designed for aircraft.
4) Reno just ended and all race winners (almost all competitive planes) are Air cooled Lyc, TCM or Pratt & Whitney. Same with Red Bull Air Races (all Lycs). The only odd ball (besides the jet class and Unlimited with Merlin V12) was the Falconer V12 in a Thunder Mustang, which came in a distant 5th. The Falconer V12 is a special race engine, not mass produced car engine. The top three panes in the Ultimate Gold race were ROUND air-cooled. Miss America P-51 came in 2nd but was DQ'ed for flying too high and cutting pylon(s).
5) You acknowledge that tinkering is part of the package of using alternative engines. Agree. I like to fly and tinker with the airframe and engine installation, cooling, baffling, 4-into-1 headers, but not the core engine and prop itself.
6) Yes I'm into engine conversions. Conversion of $30K Into a Lyc, Go Fly Guy.
However I do respect people who want to roll their own with a car engine or a Continental vs Lycoming. However I also want to warn people it is not for the faint of heart and it may not result (almost assured to not result) in superior performance or value. The MOST important is safety. Many Lycs once independent ignition and fuel system (Mags and mechanical fuel system) may not be electrically independent (ignition and fuel) anymore, as people add EI and EFI. Mechanically car engines are reliable. HOWEVER the Prop Speed Reduction (PSRU) are problematic and often mandate a fixed pitch prop or electric prop. I think both are way less desirable than a Constant Speed (CS) prop.
7) Van's Aircraft is stubbornly loyal to Lycoming? There is no stubbornness but just the best engine for "Total Performance". End of story. Also Van's is not going to supply multi cowls and engine mounts. Bad business. The RV-12 is a LSA with limits, so the Rotax is the better choice in the 100HP ball park. Personally I would use a O-200 (or IO-240) Continental. Rotax are very expensive. The Rotax Si915 is pushing $40,000. That is more than a 200HP Lycoming.
8) You make a great point however about supply demand. The EAB market made a demand for new engines to sell direct. I would add the STC market (Superior, Titan, ECI, Lyc, Thunderbolt) making Lycoming engines has kept cost way down and drove innovation in higher performance and aftermarket support in electric ignition and EFI.
9) Alternate
aircraft engines, as you mention "Continental -470 in an RV-10 or the -360 Continental (as the subject of this thread) options for the 4/6/7/8/14. The IO-240 might work well in an RV-3 and RV-9." The problem is the Lyc -320 (150 to 170HP) and -360 (180 to 210 HP) and -540 (230-350HP) are hard to beat for the money, especially the 320. It is difficult to make a case for different engines, besides you dare to be different. In the case of the -470 they are long out of production. the IO-240 for me would be my choice for an RV-12 over a Rotax, if you can buy an IO240 for less than a O320. Then the RV-12 may not be an LSA anymore (in weight, speed). My pumped up 360 I built from a used engine for my RV-7 is my thing. I personally don't see a big reason to go TCM because the aftermarket for Lyc is better, support is better for EAB kit plane builders. I will say the TCM TIO550 with single control (prop, throttle, mixture) is impressive. I can't imagine what that cost. It is way more than a Lyc IO540 with mechanical FI.
10) If you are willing to make your own engine mount, cowl, adapt a PSRU (use great caution here), buy an alternative engine, prop, do it. However I repeat don't expect to be a Lycoming killer in performance or value. None of that bothers me (being slower, heaver, less resale) but SAFETY is my main concern. There are very safe conversions, but personally it is not my cup of tea. There are also bad engine conversions. We can reinvent the wheel but it will still be round and probably a Lycoming.