Nope! One camshaft in the middle of the block.
Some info on how it all works:
Displacement on demand
The 2005 Chrysler 300C and Dodge Magnum RT were the first high-volume, modern production vehicles in North America to feature fully-functioning cylinder deactivation. The MDS (“multiple displacement system”) seamlessly alternated between fuel economy in four-cylinder mode, and power in V-8 mode. Owners receive the powerful benefit of the Hemi engine with the fuel economy that they would expect from a smaller engine.
Bob Lee, Powertrain Product Team vice president, said, "The MDS was part of the engine's original design. This resulted in a cylinder-deactivation system that is elegantly simple and completely integrated into the engine design. The benefits are fewer parts, maximum reliability and lower cost."
This system triumphs because of modern electronic controls and electronic throttle control. The HEMI can transition from eight cylinders to four in 0.04 seconds. The system works by cutting out the valve lifters, keeping the valves in four cylinders closed; energy is not lost by pumping air through them.
Fuel economy goes up by up to 20% percent under various driving conditions, with a 10% aggregate improvement. Because (as with the slant six) oil comes through the pushrods, lubrication is maintained when cylinders are at rest.
Bob Sheaves discussed why the system is almost always used on V8s and not V6s:
"An Otto cycle engine requires two full revolutions of the crankshaft to fire all the cylinders. Two revolutions x 360 degrees equals 720 degrees of rotation. Dividing that total rotation by the number of cylinders to have an even firing engine (naturally balanced) will give you 120 degrees, which means that you have a cylinder firing every 120 degrees of rotation. When you take out 3 of the cylinders, you have increased the firing rotation to 240 degreees (720/3), still balanced between each firing of a cylinder. The catch is that you have increased the harmonic vibrations as the rpms increase. Deactivation of four cylinders in a V6 would mean losing the multiple of six cylinders, which intrinsically keeps the engine in primary balance. (The lack of natural balance is why balance shafts are often used in 90 degree V6s and larger inline 4 cylinder engines.)"
Chrysler engineer Cole wrote: "The modern Hemi always shuts off the same four cylinders. In our duarability test cycle (150,000 customer equivelant miles driven at the 95th percentile, meaning that only 5 percent of our owners are more abusive than our testing), we have not found any adverse wear patterns." Even in 2010, five years later, there have been no reports of problematic uneven wear.
