Regarding Corvair flight engines, I was initially rather apprehensive. I spend a considerable amount of time researching and eventually going to a Corvair college(multiple events per year where William Wynne and SPA get together with dozens of Corvair builders to make progress, assemble, and often break in and test run their engines on the custom run stand assembly William supplies) and spending time with Dan and William at Oshkosh, etc.
I have come away very impressed with their approach and products. They go to great lengths to design, test, improve, repeat on all their products and procedures. It’s the most open, honest, and professional approach I have ever seen for an alternative engine. I have been fully prepared to do a top to bottom rebuild on an O-200 for my non RV project, it’s not about the money.
IMHO, the Corvair conversion they have developed is mature enough to be considered a very reliable direct drive engine in the 100-125hp range. And yes, the smoothness(lower vibration) of the 6 cylinder balanced Corvair is night and day better than an O-200 or any other opposed 4 aircraft engine. The exhaust tone and overall sound is really pleasant as well, a bit like a Merlin with the right headers.
I’m personally heading down the top end of the spectrum, with a new US made billet stroker crank and new rod package from SPA, going to a full 3300 (200 cu in) with the 5th bearing and all the other well developed parts. One can build a top quality 2700 for SUBSTANCIALLY less.
There have been many who have gone down their own path and developed their own conversion parts for Corvairs(such as the turbo Corvair build in the other thread). I have considered doing some of it myself. But as someone who designs and builds complicated metal parts for a living, I can’t think of a single part that I can design, test, and produce myself that would honestly be as cost/time effective as using the proven parts that William and Dan offer. If you really enjoy that kind of thing or are determined to have something unique, I get it though.
For those interested in checking them out:
https://flywithspa.com/
https://flycorvair.net/
http://shop.flycorvair.com/
George