Why not electrohydraulic or electromagnetic "camless" design with no vibration issues and easy timing changes? Has it been done? Too expensive? Too much heat and gas pressure involved?Whoa - I'm feelin' like Emily Litella! I can't believe I didn't connect those adjacent dots (re: FI vs FI)!
The gears don't *cause* vibration, but using belts somewhat isolates the valvetrain from the vibrations in the lower block (they can't transmit vibration into the camshaft itself). Gears - being solid - can transmit these vibrations into the camshaft. A caveat - this is what I learned regarding gear drives when I was building engines in the early 1980s (Ford V8s...). I guess it could no longer be an issue...