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For our next trick, we heaved on our freshly ported heads. The 360-cube test engine seemed to like them, posting 474.4 hp at 6,400 rpm, and 442 lb-ft. at 5,000, with 468 hp still on tap at 6,700 rpm. With 250 cfm on hand, the heads could have supported over 500 hp in an optimized package, which probably would have included more cam and stepping up from our 1 5/8-inch street tubes to bigger headers. The ported heads were worth a gain of 60 hp, which equates to almost 15 percent more power.