I'll have to see if I put a 55* on a spare valve if it will even leave a margin. 50* looks to have a lot of options. Guess I'll have to experiment. I was just wondering. I know there is a lot of variables bowl shape and such. Also somewhat concerned about durability. A freshen every few years ain't so bad.
I also forgot to mention the under head shape of the valve. It's critical. A nail head and steep seats don't like each other. The steeper seats are also tougher on valve faces so you want a good margin.
