Unleash Power: The 671 Supercharger Guide

In the realm of high-performance automotive upgrades, few components command as much attention and respect as the supercharger. Among these formidable forced induction devices, the 671 supercharger stands as an undisputed icon, a symbol of raw power, unmistakable visual appeal, and a deep-rooted history in the world of hot rodding and drag racing. For enthusiasts looking to dramatically boost their engine's output and create a truly show-stopping engine bay, understanding the intricacies of the 671 supercharger, both in its traditional form and with modern enhancements, is absolutely essential.

What Exactly is a 671 Supercharger?

The name '671' might sound like a cryptic code, but it actually has historical origins rooted in the Detroit Diesel 6-71 engine, for which this particular size of Roots-type blower was originally designed. A Roots-type supercharger, like the 671, operates by using a pair of intermeshing lobes (or rotors) that spin within a housing. As these rotors turn, they trap air from the intake and force it into the engine's cylinders at a higher pressure than atmospheric, effectively cramming more oxygen into each combustion cycle. This increased air density allows for significantly more fuel to be burned, resulting in a substantial increase in horsepower and torque.

Unlike turbochargers, which are exhaust-gas driven and suffer from 'turbo lag', superchargers are belt-driven directly by the engine's crankshaft. This direct connection ensures instant boost delivery as soon as you touch the throttle, providing a linear and exhilarating power curve. The 671 is particularly renowned for its prominent mounting on top of the engine, often protruding through the bonnet, making an undeniable visual statement that screams performance.

The Complete 671 Supercharger Kit Explained

For those eager to experience the thrill of forced induction, a complete 671 supercharger kit provides everything needed for a straightforward installation. Take, for instance, a comprehensive kit designed for a small block Chev engine. These kits are meticulously assembled to ensure all necessary components are included, making the upgrade process as seamless as possible for the enthusiast. The goal is to provide a 'ready to bolt on' solution, transforming a standard or crate engine into a powerhouse.

A typical complete 671 supercharger kit will include a range of high-quality components, each playing a crucial role in the system's performance and reliability:

• Weiand 671 Supercharger Unit: This is the heart of the kit, featuring a robust, CNC machined case and rotors. Weiand units are specifically engineered with exclusive two-lobe rotors, optimised to generate maximum boost even at lower RPMs, providing exceptional off-idle response and mid-range grunt. Each unit undergoes 100% boost testing to guarantee peak performance and efficiency right out of the box. The matched gear sets ensure precise rotor alignment, which is critical for smooth operation and longevity.
• Carburettors: Often, complete kits come with dual brand-new carburettors, such as Holley 600 CFM polished units, specifically 'blower referenced'. This means they are designed to work optimally under the positive pressure generated by the supercharger, ensuring correct fuel delivery and atomisation. The dual carburettor setup not only provides ample fuel but also adds to the iconic visual appeal of a blown engine.
• Air Filters: To protect your engine from contaminants while allowing maximum airflow, two high-flow air filters are typically included. These are generally sized appropriately for the carburettors and supercharger, although styles may vary.
• Intake Manifold Gaskets: High-quality intake manifold gaskets, such as Felpro, are provided to ensure a perfect, leak-free seal between the manifold and the engine, crucial for maintaining boost pressure.
• Redline Throttle Linkage: A dedicated throttle linkage system is essential for connecting the accelerator pedal to the dual carburettors mounted on the supercharger. The Redline linkage ensures smooth, synchronised operation of both carburettors.
• Billet Belt Tensioner Components and V-Belt Pulleys: These robust components are vital for maintaining proper belt tension, preventing slippage, and ensuring reliable power transfer from the crankshaft to the supercharger. A common setup might include a 34-tooth lower pulley and a 38-tooth upper pulley, resulting in approximately 11% underdrive. This underdrive ratio is a careful balance, providing a significant boost increase without over-spinning the supercharger, which contributes to engine longevity.
• Adapter Plate: An adapter plate for mounting two 4-barrel carburettors is also included, ensuring seamless integration of the fuel system with the supercharger unit.

It is important to note that specific kits, like the one described, are often designed for particular engine configurations, such as Small Block Chev engines with a short water pump. Always verify compatibility before purchasing.

Performance Gains and Aesthetic Appeal

The most compelling reason to install a 671 supercharger kit is, unequivocally, the dramatic increase in power. Kits like the Weiand 671 are engineered to generate an impressive 175-275 horsepower increase, along with a significant boost in torque, across the entire RPM range. This translates to exhilarating acceleration, improved towing capability (if applicable), and an overall transformation of your vehicle's performance characteristics.

Beyond the raw power, the visual impact of a fully polished 671 supercharger kit is unparalleled. The gleaming, CNC machined case and rotors, combined with polished carburettors and billet components, create a stunning focal point under the bonnet. This 'maximum visual appeal' is a major draw for car show enthusiasts and anyone who wants their engine bay to be as impressive as their car's performance.

The Speedmaster Individual Throttle Body EFI System: A Modern Twist

While the classic 671 supercharger setup traditionally employs carburettors, modern technology offers advanced alternatives that combine classic aesthetics with contemporary performance. The Speedmaster Individual Throttle Body (ITB) EFI (Electronic Fuel Injection) system is a prime example of this innovation. It offers the timeless 'Weber induction' look, highly coveted by enthusiasts, but brings the versatility and precision of EFI.

This system delivers crisp EFI performance, capable of supporting very high horsepower applications. Fuel and air are delivered through precision cast aluminium 50mm IDA style throttle bodies. The design of these throttle bodies is crucial, as individual throttle bodies provide superior idle characteristics and astounding throttle response. By having a dedicated throttle plate for each cylinder, airflow is precisely controlled, leading to a much more immediate and satisfying engine response compared to a single large throttle body.

The construction of Speedmaster throttle bodies is top-tier:

• Material: CNC machined, heat-treated 601 cast aluminium ensures durability and precision.
• Butterflies: Each butterfly is individually measured for its bore and precision machined to achieve exceptionally close tolerances, minimising air leakage and optimising airflow. They are secured to centreless ground brass shafts with split screws, ensuring both reliability and serviceability over time.
• Sealing: O-ring seals on the lower mounting faces guarantee a perfect, airtight seal when mounted.

The Speedmaster linkage set is another highlight, ingeniously incorporating throttle stops, idle controls, lever arms, and a joiner/balancer all into a single, cohesive unit. It features a convenient single screw adjustment for calibrating the front-to-rear throttle shafts, simplifying tuning. Furthermore, the bell crank includes a fully indexable eccentric cable pulley, which is pivotal for achieving good slow-speed drivability while still allowing for full throttle geometry at wide-open throttle. This attention to detail ensures that the system performs flawlessly across the entire RPM range.

Injector recommendations for the Speedmaster system highlight its high-performance capabilities: 50 Lbs./Hr. injectors are recommended for 700-750 HP (naturally aspirated), while 80 Lbs./Hr. injectors are suitable for over 1100 HP (naturally aspirated). While these figures are for naturally aspirated setups, they underscore the system's robust design and capacity to support significant power, making it a viable option for highly tuned, potentially supercharged, engines seeking the benefits of precise EFI control, improved emissions, and better economy through tight air/fuel ratio management.

Carburettor vs. EFI: A Comparative Look for Performance

When considering a high-performance engine, especially one with a supercharger, the choice between traditional carburettors and modern EFI is a significant one. While the 671 kit is often supplied with carburettors, the existence of systems like the Speedmaster ITB EFI opens up a world of advanced tuning and performance benefits.

Frequently Asked Questions About 671 Superchargers

What is a 671 supercharger?

A 671 supercharger is a type of Roots-type blower, originally designed for Detroit Diesel engines, that uses two intermeshing lobes to force more air into an engine's cylinders, significantly increasing horsepower and torque. It's known for its prominent, often polished, mounting on top of the engine.

How much horsepower can a 671 supercharger add?

A complete 671 supercharger kit, such as the Weiand unit for a small block Chev, can typically add between 175 and 275 horsepower, along with a substantial increase in torque across the RPM range.

What engines are compatible with the 671 supercharger kit?

Many complete 671 supercharger kits are specifically designed for popular V8 engines. For instance, the Weiand kit mentioned is engineered for Small Block Chev engines, particularly those utilising a short water pump configuration.

Can I use Electronic Fuel Injection (EFI) with a 671 supercharger?

Absolutely. While many traditional 671 setups use carburettors, modern EFI systems like the Speedmaster Individual Throttle Body system can be adapted for high-performance engines, including those with superchargers. EFI offers superior control over fuel delivery, improved drivability, better emissions, and often higher efficiency compared to carburettors.

What are the benefits of a polished supercharger kit?

A polished supercharger kit offers significant aesthetic benefits, creating a stunning, show-quality appearance under the bonnet. The highly reflective surface of the CNC machined and polished components adds to the overall visual impact of the engine bay, making it a true centrepiece.

Conclusion

The 671 supercharger, whether in its classic carburetted guise or paired with a sophisticated EFI system, remains a compelling choice for anyone seeking a dramatic boost in their vehicle's performance and an undeniable visual statement. Its heritage, combined with the raw, instantaneous power delivery of a Roots-type blower, offers an driving experience unlike any other. With complete kits readily available, transforming your engine into a high-horsepower, head-turning machine has never been more accessible. Embracing the 671 means investing in a legacy of power, style, and engineering excellence that continues to define the very best in automotive performance.

If you want to read more articles similar to Unleash Power: The 671 Supercharger Guide, you can visit the Automotive category.