I am interested to hear your reason for making the comment regarding the durability of the 1.7L 8V crank as opposed to the 1.7L 16V crank. I am running a 1.7L 16v crank in my race engine, which is 1800cc, and I am looking to build another motor but only have a 1.7L 8V crank for this engine.
Do you know if the forging details, ie strength of material, of the cranks are different? There doesn't appear to be any other differences that I can determine.
Well since the 1.7L 16V crank is nitrided, the first 0.010in of metal on the surface is significantly harder than that of a non nitrided crank, therefore it will be more resiliant to wear and can resist fatigue, especially at higher rpms. Since the 8V crank is not nitrided it can be more susceptible to these factors, but is still a strong and very good crank.
I would imagine that both the 8V and 16V cranks are identical, only one is nitrided. The strength of material for the two should be the same, they would have both gone through the same processes except the 16V got nitrided at the end of finishing.
It may be worth asking at your machine shop if you can have the 8V crank nitrided (some offer this) then you could make it just the same as the 16V one - not sure if thats a possibility, but ask anyway.
But I think the key to a good engine is not the fact that the crank is nitrided or not, but whether all the parts are balanced together - this is how stresses are kept to a minimum.
