Re: Plastic timing gears, why and for how long were they used? (mrvette)
Noise is one reason but there is another reason for the nylon teeth... If you drive long enough and neglect the oil changes the chain will get enough slack to actually jump a tooth or more. When this happens with nylon teeth, the teeth just rip off. With metel teeth this would destroy the engine as the pistons would collide with the valves. I have seen this happen and even at idle with metal toothed gears, results in bent pushrods, pulled studs, bent and broken valves. I do not like nylon toothed gears myself but they do offer a margin of safety.