my builder ported mine. He had a template for a stock based head, and took out a bunch of aluminum. He cut a bigger valve and upgraded the valve and valve hardware. 520 inches, 11:1 compression, 6bbl. 555hp 640 tq at 5000rpm. Once I got the timing dialed in and the carbs set up, no issues on 93 octane. If it is hot and I could only get 91 octane, I don't put my foot in it very deep just to be safe.