On the other hand, a typical street engine will spend 70 percent or more of its time in between peak-torque and peak-horsepower engine speeds. Few street cars hit peak horsepower rpm in the quarter-mile in high gear. While peak horsepower is interesting, it can be deceiving, as our test engine in a typical street car with a 3.55 rear gear and a three-speed automatic only experiences 6,000 rpm (or more) twice in a typical quarter-mile pass, hitting this rpm at the top of First and Second gear. This led us to one more evaluation that should shed far more light on the question of which head is the best. On the plus side, the Vortec intake port flows 42 cfm better than the stock heads at 0.500-inch lift and 18 cfm better on the exhaust side. If you are considering Vortec heads, keep in mind that swapping them in will require these parts at additional cost. In addition, you must use guided rocker arms and center-bolt valve covers, and the intake manifold bolt pattern is unique, requiring a specific intake manifold. This added roughly another $160 to the price of the heads but allowed us to use 1.6:1 roller rockers to level the playing field against the other heads in the test. We anticipated this issue and used a set of Scoggin-Dickeymodified Vortec heads with the valve guides machined for additional clearance and fitted with better, Z28-style valvesprings. In stock form, the retainers hit the seals with valve lifts above this 0.450-inch figure. The main limitation with these heads in pure stock form is their inability to utilize valve lift above 0.450 inch. These heads were only used on a few models of Vortec truck engines, but their longevity is ensured because they flow so well. The production-based iron Vortec head represents one of the best budget investments for power for the small-block Chevy.
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