Ferrea to Speedmaster exhaust valve test
Interesting & valuable information, especially for rule restricted classes, like Stock and Super Stock and some circle track engines which require OEM sized valves. Horsepower can get hard to find and the little cc gains in flow can add up to noticeable performances gains especially when combined with other improvements, regardless of how small. I forgot the details, but I believed I read somewhere that 2cc in flow is roughly worth about 1 HP.
It's kind of like wanting to lighten a car by 100 lbs. It may not be possible to find a 100 lb part to remove, \but finding 100 places to remove 1 lb is usually easier. Attention to detail and little things add up.