garfunkle

The cost delta is much more than just the material. The equipment, skill level and labor rate to work on it are also different. 321 contains less carbon than 304(or 304L) and includes the addition of titanium. This [titanium] also makes it much less susceptible to expansion/contraction from heat cycles. The titanium component of 321 is negligible when it comes to weight..... The debate also arises that some say this superior thermal characteristic is preferred while others would testify that 304[L] is better for headers because it expands and contracts as a more consistent rate with the block and gasket. I know the Porsche Cup and RSR cars use 304L but 321 also has merit. For a street car, none of this matters

spdracerut

The Cup and RSR cars are naturally aspirated though compared to the turbo 991.2 Carreras For a street car that isn't driven hard, I agree, 304L is fine. For a car driven hard, 321 is more robust. I'm surprised though that Cup and RSR cars would use 304L. Even NASCAR uses thin-wall inconel. Oh man, the old F1 super thin wall inconel headers on the 20,000rpm V8s were something else! Of course, those were only designed to last one race using extreme thin wall to save weight. And I know this is slightly derailing, but on the topic of weight savings, Gordan Murray's T.50 is an exercise in weight shaving. The pedals went through a few design iterations which removed 300 grams.