Are there companies that make experemental versions of the lycoming engine that cost significantly less.
Are there companies that make experemental versions of the lycoming engine that cost significantly less.
Are we talking about a parallel valve -540 or an angle valve engine? The parallel valve engines are lighter but more fragile in aerobatic use. Pitts fly with parallel valve -540's and Extras fly with angle valve -540's. They are not the same engine despite the "540" in their name. You have to look at what comes after the "dash" following "540".
What makes any of the IO-540's an AEIO-540 is the crank with the heavier prop flange that does not have any lightening holes in it, and the installation of the fittings for the inverted oil system. And maybe the prop governor mounted on the front left side of the case rather than the rear. If I were to go looking to build up an aerobatic engine, I might start with a used -540 that has the right crank, add an aerobatic sump and cold air induction, and install the Christen fittings.
So what do intend to do with the AEIO engine? As a weekend pleasure flyer you might not need an AEIO at all. As a competition pilot you will likely beat on the engine pretty hard and need all of the AEIO features.
Best of luck,
Wes