Blower Sizing
Selecting the right blower requires determining how large a blower your application requires, and the first step in doing so is making sense of the different nomenclature. Weiand offers many series of blowers such as 142, 144, 174, 177, 250, and 256. On Weiand's smaller blowers, the number represents the volume of air in cubic inches that the blowers move per revolution. For example, the144 series blower produces 144 ci of air per revolution. On the company's larger 6-71 and 8-71 blowers, the number refers to the original GMC labeling scheme. "GMC designed the 6-71 blower for a six-cylinder motor displacing 71 ci per cylinder, hence the name," McFarland explains. "An 8-71 was designed to feed an eight-cylinder motor displacing 71 ci per cylinder. That said, a 6-71 blower moves 411 ci of air per revolution, and an 8-71 moves 436 ci per revolution."
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Manifold Design Parameters
"Despite their simple outward appearance, countless factors such as runner volume, runner cross-section, and plenum volume must be considered when designing an intake manifold. Runner volume is a function of the charge-air passage length and cross-sectional area. The passage length determines the engine speed at which the pressure waves within the inlet passage best promote cylinder filling. Cross-sectional area is always a balance between providing velocity to aid inertial filling at the end of induction cycle before the intake valve closes, reducing flow restriction during the pumping portion of the induction cycle and providing a good pressure-wave signal to the passage inlet. Plenum size affects how the pressure waves generated by engine operation will aid cylinder filling, while plenum geometry contributes greatly to cylinder-to-cylinder air and fuel distribution. Unfortunately, the least interesting but most important factor in designing intake manifolds for the performance aftermarket is optimizing design within the packaging constraints given by vehicle applications. Other important factors are casting design, casting tooling, manufacturing techniques, and new raw materials that are now available." -Jim Dralle
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Intake Porting
"Even if you've gone through the effort of porting your heads, it doesn't necessarily make sense to port the intake manifold. A wise porter once explained that it's not the material that's removed that's important, but the material that isn't removed. Unless proper development and validation testing is performed, most intake manifolds are best left unported. Good port matching usually won't do any harm and will typically provide a 5-10hp gain. This is especially true when the flange exit size has a smaller cross-sectional area than the upstream charge-air passage, which is sometimes the case since a single manifold design must often fit several different cylinder head designs. Usually, enlarging the flange opening area larger than the upstream charge-air passage cross-sectional area will not yield any power gains." -Jim Dralle