Also a major consideration is NOISE. Most car buyers are unconcered with maintenance ease. They want QUIET! Gears are noisy in operation. Most modern production engines are so quiet that the loudest things left on them are the injectors and / or the fuel pump!

Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ> wrote:  Quoting John Rodgers :

> Just reading the post about "New Engine Conversion" - and I wonder -
> besides cost, is there any reason why engines have not had meshed
> gears
> to drive the cams. Piston type aircraft engines all have gear driven
> cams. No body wants to try to pull over and park on a cloud when a
> timing chain fails.

The only engines I know of with gear-driven DOHC are Honda's VFR and NR
bikes. reason? Expense, nothing else... excepting perhaps mass.