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The airflow capacity of both manifolds is measured using a Superflow 110 flow bench and a ported cast-iron cylinder head flowing 255 cfm at 28 inches of pressure. Testing consists of measuring the bare cylinder head, connecting it to an intake manifold, limiting airflow to a specific runner, and remeasuring. Calculating the result yields an intake-to-head flow percentage, which-after averaging eight runners-provides a single percentage for each manifold. That can then be used to predict performance effects.