Okay.....maybe outflow was the wrong word. Out perform. Is that better? Because of their quench design, they are better than all the rest....except the max wedge stuff. Fair enough?
Thats probably a fair statement. I can envision a few circumstances where the open chamber would be of benefit, such as lowering the compression to a more pump gas friendly area. I wonder too about valve shrouding in a certain area of lift, as it appeared the 915 trailed the others until a higher valve lift, and then it jumped ahead, maybe the valve finally made it far enough out of the chamber to change the flow characteristics?
FWIW, I have a set of the 516's that many despise, with the 1.74" exhaust added, and a mild bowl port with a 3 angle valve job. They flow in the 240 cfm range at around .500" lift, 28" of water. Thats a fair increase over any of the stock heads flow #'s. The fellow who ported these did tell me they take a good bit more work than the newer port designs, but if you really want the closed chamber....