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This is a derivative of one of Ford's most successful race heads ever: the D3. On a 15:1 350-inch drag race engine, it is capable of 900-plus hp from a single four-barrel configuration. The point to note here is that all the exhaust from such an output still goes through a 1.6-inch exhaust valve just as we see on a typical street 350. By contrast, the intake is almost 2.25 inches in diameter so the size bias is much more toward the intake than is seen on a low-compression engine.