Vortec cylinder heads feature a chamber shape and intake port that allow a large amount of air to mix with fuel for high air and fuel mixture velocity. The intent of GM engineers was the same as that of most builders of performance engines: to increase horsepower of the Vortec engines, as well as torque.
Because General Motors has two Vortec cylinder heads on each new truck they sell, they’re literally selling several hundred thousand heads. Selling Vortec cylinder heads at this volume gives GM the ability to spend money on research and development to improve the performance of the cylinder heads. It also makes it possible for replacement cylinder heads to be priced reasonably.
Features of the Vortec Cylinder Heads
Combustion Chambers – in a Vortec cylinder head, the combustion chamber measures a liquid volume of 64cc. Depending on what type of engine, this small size may be either a disadvantage or an advantage to the overall performance.
Size of the Valves – despite changes in other areas of the Vortec cylinder heads, valves are about the same dimensions as other small-blocks. Vortec cylinder heads have a valve stem measuring 11/32-inch in diameter, which was common before the 1970s. Most other small-block heads are now being designed with valve heads of 3/8-inch in diameter.
ValveSprings - Vortec cylinder heads have newly created “valvesprings”. These springs become damp on their own without a damper.
Intake Ports – like combustion chambers, intake ports have liquid volume measurements. The Vortec cylinder heads feature larger than average intake ports. In 1986 or earlier, traditional cylinder heads were measured to hold 160cc’s. The Vortec cylinder head holds more liquid, 170cc’s, because it was designed to have a taller intake port. By making the port taller, the overall radius of the intake port is larger, which succeeds in holding more liquid and improving the air and fuel mixture in order to maintain velocity as the air moves through. More air and fuel mixture velocity translates into higher horsepower and lower torque – meaning the goals of GM have been achieved!
Disadvantages of Vortec Cylinder Heads
One issue many car owners consider a disadvantage of the Vortec cylinder heads is that a different intake port manifold must be purchased. The standard intake manifold will not work with the head due to the taller height of intake ports on Vortec cylinder heads; and the different size and number of the mounting bolds of the intake manifolds.
Another disadvantage of Vortec heads is the valve lift limitations. If the lift exceeds .470 inches, the valveguide gets pinched between the guide and retainer. Originally, GM designed an o-ring and tin shield over the spring that would not prevent all oil from reaching the valveguide. It was thought that a little bit of oil finding it’s way to the valveguide would improve performance and act as a lubricant, therefore increasing the life of the valveguide. In 1970, a Federal Clean Air Act made this illegal, and GM had to redesign a seal that would eliminate any oil from seeping into and past the valveguide.
Vortec cylinder heads are cast iron. They’re the first of cast iron cylinder heads used for individual-port fuel injection. This eliminates the exhaust heat crossover passage which helps vaporize fuel that builds up on the intake manifold floor.