If I was to build a fairly serious street strip engine I'd shoot for 1.8 cfm per hp as a goal any hp above that be a bonus. Eg.. 500 hp / 1.8 = 278 cfm so I'd would want a head that flowed at least 280 cfm around .500-.600" lift to try make 500 hp. (Obviously with a decent overall curve .300-.600".)