They flow quite a bit better actually. The only reason I went this route is , I had the guides and the stock Magnum valves already this=FREE. I would have gone with Chevy valves had I not had these "lying around". In fact I am just finishing up a set of "J" heads right now using Chevy 2.02/1.6 valves that flow around 244 cfm FWIW. J.Rob
