7. Available with either 67 or 76cc combustion chambers, the High-Port 240cc heads come fully assembled with 2.10/1.60-inch valves, 1.55-inch dual valvesprings, and titanium retainers. The large 2.10-inch intake valve requires a minimum bore diameter of 4.125 inches. At $2,996 per pair, the High-Port castings are an exceptional value. To hit our target 11.0:1 compression ratio, we went with the larger 76cc chambers.