This engine, and others like it, has opened up a brand-new chapter in the ever-evolving, wild world of Chevrolet power. By design it has a bore and stroke of 4.60 inches by 4.25 inches and Big Chief II heads, which are about 2 inches taller, that feature oval-shaped intake ports. This, they say, is for maximum cylinder filling. Years ago, creative racers would angle-mill heads to arrive at the desired combustion chamber size and to improve the valve angle in combination with the incoming intake flow. These heads are nicknamed “11-degree” heads, as they have been designed with a built-in 11-degree angle right out of the box. There’s no angle milling needed here. A special valvetrain is necessary, along with longer stem valves. Quarter Mile Performance feels that these heads are worth 200 additional horsepower over the very best “shorter” heads.
