Don -- I've heard one of those run. Not impressed. With that many cylinders, it sounds like noise. You have to be able to hear the individual notes to enjoy the true melodic magic of a symphony. So maybe I will change my vote to a 6-71. I like listening to Grigg's 4-53T run, too.
My other choice would be a Pratt and Whitney R-985. Had one fly over the house nice and slow earlier -- pure rapturous music! (The DHC-2 Beaver from Test Pilots' School)
6 cylinder gas engines are ok, but nothing to write home about in my book. Although ... I do like following Chris Sweet's Green Machine -- the 261 on twin mufflers sounds as good as it gets (for a gas engine). But I like the sound of a 4 cylinder aircooled Boxer with tweeter pipes better ...
