- There are two main parts to most manifold designs: upper and lower. Over the years, aluminum and cast iron have been the common method of producing the upper and lower intake manifolds for automobiles. In more recent years, plastic manifolds have started appearing in more cars to reduce weight and minimize manufacturing costs. However, many of the plastic designs have received negative criticism from experts and enthusiasts alike, and, in some cases, lawsuits have appeared because of faults in the design.
- The upper manifold transfers the air and fuel mixture from a single source, which is the carburetor in older engines and the throttle body in newer models. Once this fuel and air mixture has been concentrated, the upper manifold delivers this mixture to the lower manifold, which in turn distributes the gas into each cylinder head of the motor. Each manifold design is specific to the motor in which it is paired, as the administration of the fuel and air mixture is imperative in keeping power consistent in the automobile.
- After years of abuse and irregular maintenance, the intake manifold of your engine might start to show obvious signs of wear. Replacing the intake manifold gasket is a common and relatively cheap tune-up, but if the upper manifold itself starts deteriorating, then replacing this part is important in keeping your engine running well.
- For enthusiasts looking to replace the upper manifold to gain more performance, upgrading to a larger throttle body or carburetor and intake system is strongly recommended. The upper and lower intake manifolds are usually sold as one piece, and switching these parts out can be done in a few hours with the right tools and direction. In carbureted engines, the manifold is accessible by removing the air filter and carburetor, then labeling and disconnecting the electrical wiring and hoses that attach to the manifold. In newer engines that rely on electronic fuel injection, getting to the intake manifold is a bit more of a task, since these engines are developed for compactness and fuel efficiency more so than engine accessibility.