The 272 degree Energizer has a somewhat smooth idle, only a hint of a lope when cold. Excellant off idle performance up to 5500 rpms. When the engine's warmed up , you'd swear it had a stock cam. My 390 is just about completely stock, even has it's original 10.5 to 1 cast flat tops, C8AE-H heads, only thing I changed was the intake, swapped to a 428PI aluminum one, topped with a Holley 750 and added a set of FPA headers.