OEM valves are sodium filled to reduce heat. MOST aftermarket valves will not be. There are a few things to pay attention to with aftermarket valves. The material that they are made of dictates a lot. All valves are forged unless they are very cheap, but what is used that is forged makes a lot of difference. Your basic forged steel, then aluminum, then different grades of aluminum, then inconnel aluminum, then titanium. I highly doubt that you can touch a set of Ti valves for under a grand. Many companies nitride coat their valves to make up for the lower quality. This is fine as far as heat is concerned, but it adds mass. You have to keep in mind that your OEM sodium filled valves have there massed reduced by 30%, thus the point of sodium filled valves...on top of cooling effect. When you go back, you are adding that mass. Most aftermarket sodium filled valves range anywhere from 32-50/each. What most race valves do is thin out the lower half of the stem. This reduces the mass, while also reducing turbulance in the chambers. Most valves will be concave. If you plan on running very high compression, 13:1 or more, you will want flat faced valves for two reasons. You can maximize valve/piston clearance, and you get the most out of the compression. This adds more mass, so it has to be reduced somewhere else as well. Keep in mind a lot of what I am telling you will not have ANY effect on your engine turning 6500rpms. It will matter on a Honda at 10k rpms.
Wes
