Everything you ever wanted to know about Corvair engines
http://www.flycorvair.com/

I've read that Bernie Pietenpol never used anything else after he tried one
on a Piet. Forged crank, been flying since the early '60's. Nobody has ever
seen a cracked jug or broken crank. Much smoother than a 4 cylinder. Lots of
really cheap parts available from
http://www.corvair.com/user-cgi/pages.cgi?category=home



I picked up a running Corvair engine for $50, Machined a prop hub, and that
was all that was needed to get one running on my airboat. Not optimum, but
good enough to work. You can spend a lot of money, or almost none at all.