instead of having a single camshaft doing all the opening and closing of the intake and exhaust valves. A Dual Overhead Camshaft is cheaper to tune because in a SOHC, you need to grind a whole new camshaft to change the power/economy/emissions. In a DOHC, all you gotta do is change to timing on the exhaust camshaft if you wanna change power/economy/emissions settings. Also, 2 camshafts are smaller and lighter than 1 big camshaft. so it's lighter because it uses less metal, and it's less work to turn two little camshafts vs. a big heavy camshaft.My Chrysler 300M is a SOHC but it's got 24 valves, so it still breathes but it's got less parts than a DOHC so it's cheaper to make. And nobody is gonna be modifying the breathing on a Chrysler.The other big thing is the sparkplug. it sits in the middle of the DOHC so it fires in the center. The SOHC has to fire the plug from an angle.