I've made a few prototype valves out of 416 SS & very happy with how it machines. I just now realized I need to order more material for the real thing. Doing a bit of research on the forum I see 303 seems to be the favored alloy for valves on several respected engine builds. I presumed it was because of better corrosion resistance despite slightly lower machine-ability rating. But when I got looking at the actual corrosion difference between the two, I'm having difficulty seeing the big difference beyond the somewhat generic recommendations. In particular, have a look at my annotated corrosion rate vs Chromium. They seem quite similar to one another. Has anyone made valved out of 416 & encountered adverse issues they had not experienced with 303? Maybe 303 is just easier to obtain for folks? I'll be running a methanol engine so corrosion will be more of a factor than gasoline all things equal, so leaning towards 303 just for that reason alone. More just wondering what your experience has been.