Question for the mechanics: Plastic cam belt pulleys/drivers on 308's & Mondials

I have been working on Ferrari engines for 20+ years and have yet to see a plastic pulley fail. It might happen, I just have not seen it.
Take that for what it is worth.

I believe the aluminum would wear quickly. I have seen that on race engines I have worked on. Good old steel or plastic is what I would use if I ever needed one.

 

I'm with Wade on every count.

I have seen people break the fences off during repairs or servicing but they do not do that on their own.

They do wear but I thinK alloy pulleys wear more. Even though we usually change belts due to age they seem to wear less on the plastic surface.

 

The flange is at risk of breaking on the fiberglass pulleys over the steel ones. But as Rifledriver has noted it's not due to normal use, the belt does not have the lateral force to cause this, however when someone installing belts uses the fence as a pry point, well that puts it at risk. The potential issue now is simply age, fiberglass and plastics at this age have out gassed a fair amount and are becoming more brittle as well as shrinking. The 'plastic' pulleys will eventually fail for no other reason then age. The steel ones don't have the obvious problem.

Aluminum pulleys need to be made of 7075 and have a mil-spec hard anodized layer. At that point the steel will wear before those will. Unfortunately due to cost some may use 6061 and a std anodized layer. Those don't last.

My pulley design uses 7075 mil-spec hard anodizing. I also changed the belt profile to the more modern GT2. No risk of 'ratcheting' or tooth jump. If one has ever seen the harmonics at 7k+ rpm on the belt it's a wonder it doesn't slip a tooth.

 

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