Plastic timing gears, why and for how long were they used?
I know some years of the 350 V8 had these plastic timing gear or gears, but what years used them and why? how long did they last on average? I've heard something about noise, but a gear can't make that much noise? can it? :rolleyes:
Re: Plastic timing gears, why and for how long were they used? (killain)
GM used plastic gear teeth over aluminum/steel centers on all their cam gears across the lines that I know of...since the early 60's....it's said it was for quieter operation...but in fact I have NEVER heard the steel equivalent make noise one little tiney bit....
frankly I think it was done to sell something in 60k miles...equivalent to 6 years average driving....to force a trade in....planned obsolescence....not that there weren't plenty of other failures built in...but this one fails just like clockwork....the rest are all over the map.....
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.