duration has more to do with lopeyness ( spelling ? ) if you have an engine with a stock automatic trans and converter then you will not be able to run much more than a cam with a duration of 280 or so .. and it will not rattle windows as you wish .. if you have a high stall or a stick shift and want a rumpity idle then go for a duration more than 300 degrees .. i`ve never ordered a low duration high lift cam so i dont know what it would sound like .. i always order high duration cams and the lift is whatever it is ..