What are the pro's and con's of all three styles?

 

Gear drive...shouldn't ever have to be replaced and is very accurate, but noisy.

Belt drive...the quietest but tends to wear out and break if not properly maintained...on many motors this will cause catastrophic damage. The only motors with a timing belt that I've seen that won't do this (non-interference), were the Chrysler 2.2L/2.5L motors. Also will stretch over time, thus changing timing slightly.

Chain drive...a combination of the above. Won't break but will stretch over time and can become inaccurate. Much quieter than a gear drive (no whine of teeth meshing together) but a bit less quiet than a belt drive.

 

so a gear drive would be the best other than noise wise? so if noise is not a factor a gear drive would be the best choice?

 

For most applications, timing chains are the best route. A double roller timing chain is going to be the cheapest and will last a very long time in most cases.

Gear drives provide the absolute rock solid timing. There is nothing to stretch or wear out, short of breaking some teeth. However, like said, there is a gear whine. Also, it is possible that the vibrations emitted by the gears can mess with the knock sensor. I've never used one personally, so I don't know.

Belt drive, the best of the best. The pros are they are for the die hard racers. They emit the least about of noise or vibrations. The downsides: breakage and cost. Also, keep in mind, often times a special timing cover is needed (wet belt drive). So road matter may cause damage to a dry belt system.

My advice: double roller timing chain, like a Cloyes, Comp, something.