The IO520 is hands down the worst piston engine I've ever had the displeasure of meeting. Literally the ONLY good thing about it is that it is (subjectively) a smoother running motor than it's gray-painted counterpart. And that only applies until you blow a hole in a cylinder head (
@Capt. Chaos). I would be pretty happy, actually, if the FAA grounded the whole 207/IO520 fleet on account of being a gigantic pain in the ass. The awesome part is some masochist in Anchorage developed a fancy pants tuned exhaust that makes disassembling the engine to change a jug an even bigger pain than previously and for some unfathomable reason they are ludicrously popular up there (clearly, not being purchased by the poor sumbitches who actually have to bust their knuckles getting to the fracking exhaust nuts)