Ok, I’ll start. I needed 9 more points of smoothness to make the perfect 8000cc V8 yacht motor. My cc’s originally game from a long stroke, and small bore. I switched to a large bore and short stroke, and got an extra 6.5 smoothness points. Still need 2.5 points though.
Use a heavier flywheel until you either hit the maximum weight limit or you start seeing your power figures drop.
I had the heaviest flywheel from the start, since i wasnt worried about hp or reaponsiveness in that scenario.
Use lighter internals: e.g. pistons.