[Adger Smith]

John,
When you go to buy valves the most important thing is the material being good enough for your application. There are many, grades of Stainless Steel. Some are only good enough to be used in street cars and some cheap SS valves are still 2 piece. You have to be careful. Go to the Manley site. They explain it pretty well. Even when buying from a "Major NAME" company you need to know what you are getting. Most of them sell a low end line just to be cost competitive. You might want to consider working with a good head shop to determine what design valve you need. On my flow bench I've seen flow loss in some applications with the cut down neck (pro flow) valves. I've also seen them increase flow in some applications. Call a couple of the Name brand suppliers and ask what they have for your application. I hope this helps.