Hose clamp Induction elbow Induction risers Throttle body Hose Balance crossover tube Induction riser Intake manifold tube Intake manifold tube Throttle body Induction manifold assembly Hose Intake gasket Figure 3-6.  Location of air filter. Figure 3-4.  Downdraft balanced induction system. Figure 3-5.  Location of a carburetor heat air valve.  3-3 Figure 3-3.  Updraft induction system.  to stop dust and other foreign matter from entering the engine  through the carburetor. The screen consists of an aluminum  alloy frame and a deeply crimped screen, arranged to present  maximum screen area to the airstream. There are several  types of air filters in use including paper, foam, and other  types of filters. Most air filters require servicing at regular  intervals and the specific instructions for the type of filter  must be followed.  [Figure 3-6]