Big or Small?
"Since each motor is different, it's hard to generalize how much power a blower will add, but here are some basic points of reference. Our smaller blowers on a stock small-block Chevy running 6-7 pounds of boost will result in an increase of approximately 100-120 hp. Add a mild blower cam and a larger carb, and you can expect a typical small-block to produce anywhere from 360 to 400 hp. With a good set of heads, you can reach 440-470 hp. Upgrading to a larger blower such as a 6-71 could push the output to well over 500 hp. It's important to understand that an engine does not know what size supercharger is bolted to it. The boost produced by the blower is a bigger factor than the actual size of the blower. So the estimates above are somewhat typical of any Weiand blower. An important characteristic worth noting is that at low rpm, smaller blowers typically produce more torque than bigger blowers. Conversely, at high rpm, larger blowers produce substantially more power than smaller blowers." -Jay McFarland
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Tunnel-Rams
If not for the fact that most people expect intake manifolds to fit under the hood, then all motors would have tunnel-rams. Dralle says that the best inlet duct for a given engine will have uniform charge-air passages with the correct length and cross-sectional area and a passage inlet geometry that is straight with minimal wetted surface area. "Due to the packaging considerations for most passenger cars and race cars, dual- and single-plane carbureted intake manifolds are designed to perform best within the compromises created by packaging constraints," Dralle explains. "A tunnel-ram style intake manifold can be more closely designed to the optimum inlet duct geometry and is often considered the ideal design for maximizing power and torque."
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Blower Tolerances
Although they've evolved quite a bit, roots-style blowers look very similar from the outside as they did decades ago. However, most of the significant technical innovations that have been made since then aren't noticeable to the naked eye. The product of state-of-the-art CNC machines and the manufacturing of brand new components, Weiand blowers can hold much tighter tolerances than roots blowers from the past. This allows the lobes to fit much closer to the case, which dramatically improves efficiency. "You want to ensure the parts you are using are machined to exacting tolerances," says McFarland. "If not, you will lose boost pressure. The rotor-to-rotor and rotor-to-endplate clearances are very critical, and each blower is hand-assembled with all critical clearances being checked and recorded. They are also tested in our supercharger test cell, which measures boost pressure and airflow at varying speed points up to maximum rpm."