I will check with him. My Ritter W5'S are supposed to flow 330 cfm at .600 and the heads that Brett has now were supposed to be 337 at. 600 according to Larry Smith. I'm hoping that they improve some with the 8mm stem valves. As of today I have 3 pairs of W5'S. I wanted to make sure that at least one set of them were usable. It turns out that all 3 sets of them are good. So I'm selling one set today.