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To obtain a compression ratio in the 11.5:1 range, the heads were milled down 0.030 inch, reducing the chamber size from 65 cc to an even 60 cc. About the chamber: Mamo called it an "efficient heart-shaped design that helps low and midlift flow." Below about 0.400-inch lift, the chamber is more important than the port in promoting flow, since the mixture must get past the valve. After that, the valve is farther away, and the chamber is less critical.