lobe centers get open up for nos and a blower i looke at dur and cl more than lift for a car or truck with some cr i like to see a cam on 106 or 110 ls if the car or truck has low cr i look at 110 to112 sL but it has alot to do with the application i look at cam i have used in the past and look at five cam books and think about useable rpm spread good flowing BIG PORTS can take more cam lift and dur but evey thing gose up to CR RPM cfm and bigger headers i like smaller ports heads with good are speed