More Info
I found this here:
http://www.avweb.com/news/columns/189629-1.html
"Lycoming Continues to Push the IO-390
Over at the Lycoming booth was the IO-390-X on proud display. At the moment, the engine is available only for Experimental aircraft through Barrett Precision Engines. It is a large-bore version of the familiar angle-valve IO-360 that's rated at 210 horsepower. Monty Barrett, owner of BPA, told me that, "I don't want to overestimate the power of this engine, but I've had several on my dyno and they've all been at or above rated power." Why is this a big deal? Because many engines you and I fly with today are over-rated for power. "In fact, we've found that the 200-hp version of this engine [the IO-360] often doesn't make that much," Barrett says.
I asked the Lycoming guys about certifying the IO-390 and they said that it would take an airframe manufacturer wanting it for original equipment before it made sense to certify. I thought for a moment about the possibilities and admit they are relatively few. Piper could use it to pump up the Arrow, of course; but I doubt Mooney would see the value in resurrecting the much-loved M20J/201 model as a platform. (Particularly not when it's doing better every week selling Ovations with the Garmin glass panel.)
That said, the IO-390 makes a lot of sense for homebuilders. With the RV series as almost the de facto Experimental in 2005, the engine would have a large audience. It will fit into the RV-7 and RV-8 airframes where the IO-360 is now a popular option. VanGrunsven doesn't strictly approve the IO-390 because it's more powerful than the engine he used for flight testing of the airframes, but cautious homebuilders could always derate the engine. Word from builders who have used the 390 -- as well as hopped-up versions of the 360 -- is that the RV airframe will handle the power just fine. The 390 would also find a comfortable home in the Glastar Sportsman, which is now flying with an O-360 of 180 hp.
But Lycoming, despite having to deal with crankshaft woes and lawsuits, is supposedly poised for aggressive maneuvers for Experimental aircraft. I couldn't get the Lycoming reps to bite, but I'd say that by Oshkosh we'll have a lot more news from Williamsport. "