A look at the chart shows that the AFR heads shifted the power curve up by nearly 1,000 rpm. Look closely and you will notice that the jump in power is much better than it first appears. Down low, power differences are somewhere around 15 to 25, while upper rpm differences are more like 40 to 50. If you are building a tow rig that never sees action above 4,000 rpm, the Vortec heads keep the powerband low and torquey. However, if you plan on strip time or even a blast with the guy in the next lane, you see the AFR combination will clearly outrun the Vortec engine because its power curve is more within the realm of where your engine will operate at full-throttle. The next time you are in your car, stab the throttle and look to see where the engine does most of the pulling. It will most likely be somewhere upward of 4,000 rpm, even with a stock converter.
When converting from a Vortec cylinder head top-end assembly to a conventional small-block induction design, make sure to have several things on hand before you begin. You will need standard intake manifold gaskets, as well as a standard-bolt-pattern intake manifold. The standard intake requires 12 bolts, but the Vortec intake only uses 8. The Vortec cylinder heads do not use guideplates because they incorporate self-guided rockers. Conventional performance cylinder heads typically use guideplates (like our AFR's), which means that guideplates and self-guiding rockers cannot be used together. The last detail is perimeter-style bolt-down rocker covers. All pieces are relatively the same price between Vortec and non-Vortec designs.