A DOHC, or Dual Overhead Camshafts, engine has two cam lobes per cylinder head for intake and exhaust valves. The camshaft is placed in the cylinder head with a belt connected to it that drives the intake and exhaust cams on their respective sides of the head. With this setup, there are no pushrods or rockers to be installed on the block like a SOHC engine does. A DOHC engine has two camshafts per cylinder head; one controlling intake valves and another controlling the exhaust valves. This reduces valvetrain inertia more than SOHC engines since there are fewer moving parts, theoretically allowing it to rev up faster because less weight needs to be accelerated/decelerated during operation. It also improves volumetric efficiency by making use of resonance effects (a phenomenon where a system's volume is increased due to periodic motion). A SOHC (Single Over Head Camshaft) engine only has one cam lobe per cylinder head for intake valves because these valves are powered by the camshaft with pushrods. In a SOHC design, however, almost every component is shared with at least one other combustion chamber, which adds cost-weight compared to an overhead cam layout that separates components into individual cylinders. According to used car dealers in Wellington, the most obvious difference between a DOHC and SOHC is that the former has two cam lobes per cylinder head while the latter only has one lobe per head. There are also differences in valvetrain components. A DOHC engine requires an intake manifold, exhaust manifolds, and timing belt or chain, all of which add cost to manufacturing compared to a simple cast-iron block for an SOHC design. The increased complexity of a DOHC engine comes at a price though; it can be more expensive than its counterpart when you take into account multiple valve springs, rocker arm assemblies (as well as their corresponding shafts), bearings, seals, gaskets etc, as well as additional sensors. Hence before looking for new or used cars for sale in Wellington, it is better to check which type will be more suitable and cost effective.