So... Does anyone flying a normal flat LyConti style engine use less than full power for takeoff?
Yes -- to demonstrate high DA conditions, especially in over-powered birds.
As a demonstration, sure - But you're not doing it as a matter of regular procedure to try to extend the life of the engine, right?
Pipeline and fish spotters "loitering" engines at low MP can have cylinder problems because the pressure created during the burn cycle isn't high enough to push the rings outward and keep them sealed up nice and tight to the oil film layer on the cylinder wall in some engines.
Lots of blow-by, the cylinders don't like it, and the oil "scraper" ring ends up not doing its job, etc. Definitely a "known issue" with the O-470.
Highest MP and lowest RPM that makes a BOOK power number that you want, is the best treatment for big "sloppy" engines like our 471 cubic inch beast. Worries about "oversquare" operation are unfounded in the O-470, unless you're "off the chart" in the POH, and most over-square worries in many engines are often left over from all the way back to bolted-on cylinder engines of yesteryear instead of our cylinders that are screwed on. You'd blow the bolts off with the higher pressures.
If it's in the POH table for on O-470, it's an approved power setting unless otherwise placarded. (Some installations of O-470 engines on some aircraft have a range where the prop governor or other components have problems and there's a "skip" in the green arc on the RPM gauge, where the engine shouldn't be operated continuously.)
Picking the percentage of power you want and then using the line in the table which has the highest MP and lowest RPM, has the ring seating benefit, as well as over the long-haul treats your bottom-end the best, in the O-470. Less revolutions of the crankshaft for the same power is always a good thing, wear-wise. Plus if you're paying by tach time as all owners are for maintenance, that's an indirect benefit to your wallet, too.
So, if you have to "loiter" at low MP with an O-470, you're going to be replacing jugs sooner than you expected to. The bottom-end will probably be fine, as long as you're not taxiing it around at low RPM without enough oil being "splashed" down from the galleys above onto the bottom-end.
Most of the lower half of the engine is oiled via whatever falls from above. 900 RPM with 55 lbs of oil pressure is a nice bath. Lower on either, stuff may or may not being adequately lubricated very well.
Really low idle is the worst. Oil pump can't regulate well turning that slow, the pressure falls, oil galleys just aren't getting as much oil, and less oil is being flung around to hit all the "stuff" in the low end and cool it as well as lubricate it all. Hot summer days, I see folks pull engines way back to super-low idle while waiting for takeoff clearance or prior to run-up, thinking they're "saving" the engine from heat, and instead, they've just starved it for oil flow.
Anyway, you just have to know your specific gear and how it's built to do what it does. Much of that info is difficult to find, or buried in Service Bulletins and Service Letters that came out decades ago and aren't always readily accessible to people without some sort of "subscription" to them. I've got piles of SB numbers I'd love to read, but can't find from Continental. Especially older superseded ones that had good info, but they don't want people reading and not knowing there's a newer version. The lawyers make them pull them down from public view. Old mechanics often have them in paper format on their bookshelf.
Pro airline pilots sit in hour after hour of "systems" training on their birds, but we little guys often have far fewer options to get the information. The type clubs usually gather this type of info into a single, usable, form... if your aircraft was popular enough to even have a strong type club.
