valvetrain
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.
Thirty-five years and $636 ago, we bought an 80,000-mile ’62 fuel-injected Corvette in Fresno, California. Sadly, the car had been stolen once. The fuel injection was gone as well as the T-10 four-speed transmission. A pair of bare 461-X heads was in the trunk. The engine was found to have a rocking rear cam bearing, which caused oil to shut off to the rocker arms at high rpm. At the time, the prognosis was that it could not be fixed, so the motor was replaced with a ’68 350hp 327. Since 1976, the car has been in storage, along with the original engine.
