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Porting the cylinder head returns the most performance for the dollar spent, especially if the camshaft and intake manifold are also changed. The three areas where a cylinder head can be ported are: the bowl (which is the area behind the valves); the runners; and the combustion chamber. The largest gain in airflow is achieved by blending the bowls, along with a good valve job. Bowl blending, or pocket porting, is used to match the final angle of the valve seat with the bowl of the cylinder head. This service is essential when a hardened seat is installed, since the cutter leaves a radius that chokes airflow.