> is there any reason why engines have not had meshed gears
>> to drive the cams.

Remember when the Beetle was starting to take off in the US?
Renault (then pronounced ree-nall-t....) brought in their
competitor--the Dauphine.  Rear-engine, inline 4, water
cooled. 4-door.  It used a gear--some kind of synthetic/fiber
material.  Perhaps it was chosen because it wasn't noisy.
It wasn't chosen to hold up to starting in sub-zero temps
in Denver....  Ask me how I know.  ;-)

Richard
Boulder