The 5.7 Hemi engine is an overhead cam design, meaning the valves are actuated by camshafts located above the cylinders within the cylinder heads. The pushrod design was used exclusively on Chrysler V8 engines prior to 2003, but with the introduction of their 5.7L Hemi V8 in 2003 they switched to an overhead cam (OHC) design. This new OHC setup featured four valves per cylinder and variable valve timing (VVT). The OHV/pushrod-style engine had a single camshaft mounted in the block that actuates rocker arms that open and close the valves via pushrods connected to lifters residing in the block. Although more complex than a traditional pushrod setup, this overhead cam configuration provides superior performance and fuel economy as well as reduced emissions compared to its predecessor.