What Is A Screw Blown Hemi

What Is A Screw Blown Hemi

In the roaring world of high-performance engines, where power and precision collide in a symphony of mechanical mastery, there exists a legendary beast known as the Screw Blown Hemi.

It’s not just an engine; it’s a thunderous symphony of brute force and meticulous engineering, a heart-pounding testament to the relentless pursuit of speed.

A force of nature harnessed under the hood of a beastly machine, a technological marvel that turns mere mortals into speed demons and racetracks into thunderous battlegrounds.

The Screw Blown Hemi is not just a piece of machinery; it’s a revolution, a relentless force of nature that leaves its mark wherever it roars to life. So, prepare to dive headfirst into the intoxicating world of this automotive marvel, as we uncover the secrets and sensations of the Screw Blown Hemi.

What Is A Screw Blown Hemi

Table of Contents

What Is A Screw Blown Hemi

A Screw Blown Hemi is an advanced and potent engine configuration that blends the legendary Hemi engine design with the force-feeding capabilities of a screw-type supercharger.

This combination creates exceptional power and acceleration. Hemi engines are known for their efficient hemispherical combustion chambers, while screw-type superchargers forcibly compress air for enhanced performance.

The result is a powerhouse engine celebrated for its incredible horsepower, instant torque, and iconic engine roar. Screw Blown Hemis are a top choice for enthusiasts seeking unrivaled automotive performance.

Understanding the Hemi Engine

The Hemi engine, short for hemispherical engine, is an iconic and historically significant powerplant in the world of automotive engineering. Its roots trace back to the early 20th century when engineers sought to optimize combustion chamber design for improved performance.

The term “Hemi” is derived from the engine’s distinctive hemispherical combustion chamber shape, which sets it apart from other engine configurations.

Historical Background of the Hemi Engine

The concept of the Hemi engine began to take shape in the early 1900s, with engineers like Harry Ricardo and Sir Harry Ricardo pioneering innovations in combustion chamber design.

It was the Chrysler Corporation in the 1950s that popularized the Hemi engine with the introduction of the Chrysler FirePower V8 engine. This marked a significant milestone in the evolution of automotive powerplants, leading to an era of high-performance and iconic muscle cars.

Key Characteristics of a Traditional Hemi Engine

One of the defining features of a traditional Hemi engine is its hemispherical combustion chambers, which enable optimal airflow and fuel mixture distribution. This design contributes to improved combustion efficiency, resulting in enhanced power output.

The valvetrain in Hemi engines typically employs an overhead valve (OHV) configuration, utilizing pushrods and rocker arms to actuate the valves.

This design, while simpler than overhead camshaft (OHC) systems, still allows for precise control over valve timing and contributes to the engine’s performance characteristics. Additionally, traditional Hemi engines are known for their high compression ratios, which further boost power and torque output.

Advantages and Drawbacks of Hemi Engines

Hemi engines offer several advantages that have solidified their place in automotive history. Their hemispherical combustion chambers allow for efficient and thorough air-fuel mixing, resulting in improved combustion efficiency, higher horsepower, and superior torque.

Their iconic status and historical significance have made Hemi engines a symbol of American muscle and performance.

Hemi engines also come with certain drawbacks. Their complex manufacturing and design processes can lead to higher production costs. Additionally, the pursuit of high performance often sacrifices fuel efficiency, making Hemi engines less economical in terms of fuel consumption.

Emissions concerns have also arisen, as these engines can produce higher levels of pollutants compared to more modern, efficient power plants. Furthermore, the physical size of Hemi engines can limit their applicability in some vehicle designs, which favor more compact and space-efficient engine configurations.

Supercharging and Forced Induction

Supercharging and forced induction are integral concepts in the realm of automotive engineering, particularly in the pursuit of enhancing engine performance.

These technologies involve compressing the air that enters an engine’s combustion chambers to increase the amount of oxygen available for combustion, resulting in more powerful and efficient operation.

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Introduction to Supercharging and Forced Induction

Definition and Purpose: Supercharging and forced induction refer to the process of pressurizing the intake air to boost an engine’s performance. The primary objective is to increase the air density in the combustion chambers, allowing for more fuel to be burned, and resulting in higher power output.

Historical Development: The roots of supercharging and forced induction can be traced back to the early 20th century when engineers began exploring ways to improve engine efficiency. Developments in these technologies have played a pivotal role in the evolution of high-performance engines.

The Role of Forced Induction in Enhancing Engine Performance

Increased Air Density: Forced induction, whether through superchargers or turbochargers, significantly increases the amount of oxygen available for combustion. This leads to a more potent air-fuel mixture, resulting in improved power and torque.

Boost Pressure: Forced induction systems operate by compressing the incoming air. The pressure generated is referred to as “boost pressure.” Higher boost pressures can lead to substantial power gains but also require careful engineering to prevent engine damage.

Efficiency Benefits: Forced induction can enhance engine efficiency by extracting more energy from each combustion cycle. This can lead to improved fuel economy, provided that the engine is appropriately tuned.

Different Methods of Forced Induction

Supercharging: Superchargers are mechanically driven devices that force more air into the engine by using a belt connected to the engine’s crankshaft. They provide instant power and are typically more linear in their power delivery compared to turbochargers.

Turbocharging: Turbochargers are exhaust-driven forced induction systems. They use exhaust gases to spin a turbine connected to a compressor, which compresses the intake air. Turbochargers offer excellent power potential but may exhibit turbo lag, where power delivery is delayed until the exhaust gases spool the turbine.

Twincharging: Some high-performance engines utilize both supercharging and turbocharging to combine the advantages of both systems. Superchargers provide immediate low-end power, while turbochargers supply additional power at higher engine speeds.

What Is A Screw Blown Hemi

Screw Blowers in Automotive Context

Screw blowers, also known as screw superchargers or twin-screw superchargers, are an integral component in the pursuit of maximizing engine performance in the automotive world.

These devices play a significant role in delivering pressurized air to an engine’s intake, thereby increasing power and torque output. Understanding screw blowers in an automotive context is essential for comprehending their application in Screw Blown Hemi engines.

Definition and Explanation of Screw Blowers

Screw Blower Function: A screw blower is a type of forced induction system designed to compress and deliver air into an engine’s intake manifold. It consists of a pair of intermeshing helical rotors, or screws, that draw in, compress, and discharge air into the engine’s intake.

Helical Rotor Design: The key to a screw blower’s operation lies in its helical rotors. As these rotors spin, they trap air between them and progressively compress it before expelling it into the engine. This design results in efficient and consistent air delivery.

Historical Development of Screw Blowers in Automotive Applications

Early Applications: Screw blowers have a history dating back to the early 20th century, primarily in industrial and mechanical applications. However, their utilization in the automotive context gained prominence in later decades as engine performance became a focal point.

Adoption in Racing: Screw blowers found a niche in motorsport, particularly in drag racing and other high-performance disciplines. Their ability to deliver a high volume of pressurized air quickly made them a favored choice for achieving impressive power gains.

Key Features and Components of a Screw Blower System

Rotor Design: Screw blowers feature two helical rotors that vary in size and configuration depending on the manufacturer and application. These rotors are precision-engineered to create the desired compression and airflow characteristics.

Intake Manifold Integration: Screw blowers are typically mounted atop the engine, directly connected to the intake manifold. This integration allows for the efficient delivery of compressed air to the engine’s cylinders.

Intercooler: Many screw blower systems incorporate an intercooler to cool the compressed air before it enters the engine. Cooler air is denser and contains more oxygen, enhancing combustion and reducing the risk of detonation.

Belt Drive System: To power the screw rotors, a belt drive system connects them to the engine’s crankshaft. This linkage ensures the rotors operate at a speed proportional to engine RPM.

Advantages of Using Screw Blowers in Engines

Immediate Power: Screw blowers offer instantaneous power delivery, making them ideal for applications where rapid acceleration is crucial, such as drag racing.

High Efficiency: Their helical rotor design enables consistent and efficient air compression, resulting in improved engine performance without excessive heat generation.

Customization: Screw blower systems can be customized and tuned to suit specific engine and application requirements, offering flexibility to automotive enthusiasts and racing teams.

Screw Blown Hemi Engines

Screw Blown Hemi engines represent a pinnacle of automotive engineering, combining the iconic Hemi design with the power-enhancing capabilities of screw blowers.

These engines are celebrated for their exceptional performance, making them a formidable force in racing and high-performance automotive applications. This section delves into the specifics of Screw Blown Hemi engines.

Explanation of a Screw-Blown Hemi

Definition: A Screw Blown Hemi engine is a high-performance powerplant that marries the traditional Hemi engine’s design, characterized by hemispherical combustion chambers and an overhead valve (OHV) configuration, with the addition of a screw blower or twin-screw supercharger.

Integration of Screw Blower: In a Screw Blown Hemi, the screw blower is typically mounted on top of the engine, directly connected to the intake manifold. This configuration allows the engine to draw in and compress a significantly higher volume of air, optimizing combustion efficiency.

Evolution of Screw-Blown Hemi Engines

Historical Context: The development of Screw Blown Hemi engines can be traced back to the mid-20th century when racing teams and engineers sought to push the limits of engine performance.

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Innovations in supercharging and screw blower technology were integrated into Hemi engines to achieve extraordinary power gains.

Racing Pedigree: Screw Blown Hemi engines have a storied history in motorsports, particularly in disciplines like drag racing, where their exceptional power delivery and reliability have made them dominant forces.

Notable Manufacturers and Models Featuring Screw Blown Hemi Engines

Chrysler Corporation: Chrysler has been a prominent manufacturer of Screw Blown Hemi engines, with models like the Dodge Challenger SRT Demon and Dodge Charger Hellcat featuring these powerplants. These cars have garnered attention for their record-breaking performance on both the street and the drag strip.

Other Manufacturers: While Chrysler is renowned for its Hemi engines, other manufacturers have also explored the integration of screw blowers into Hemi-style engines to create high-performance variants. These include Ford, General Motors, and specialty aftermarket tuners.

Performance Benefits of Screw Blown Hemi Engines

Exceptional Power Output: Screw Blown Hemi engines are known for their extraordinary power output, often producing well over 1,000 horsepower in modified forms. This power enables rapid acceleration and high top speeds.

Torque and Low-End Power: The combination of a Screw Blown Hemi and a screw blower provides substantial low-end torque, ensuring strong acceleration and responsiveness at any RPM.

Reliability: Despite their immense power, well-engineered Screw Blown Hemi engines are known for their durability and reliability, making them suitable for both street and track use.

Design and Mechanics of a Screw Blown Hemi

The design and mechanics of a Screw Blown Hemi engine combine the iconic Hemi architecture with the sophisticated components of a screw blower.

This fusion results in an exceptionally powerful and efficient powerplant known for its high-performance capabilities. This section explores the intricacies of the design and mechanics behind Screw Blown Hemi engines.

Overview of the Internal Components

Hemispherical Combustion Chambers: The foundation of a Screw Blown Hemi engine is its hemispherical combustion chambers, which promote efficient airflow and combustion. These chambers are characterized by their dome-shaped design, allowing for optimal fuel-air mixing and power production.

Valvetrain: The valvetrain in a Screw Blown Hemi retains the overhead valve (OHV) configuration, consisting of pushrods, rocker arms, and two valves per cylinder. This design provides precise control over valve timing and ensures compatibility with the Hemi architecture.

Screw Blower: The key addition to the Hemi engine is the screw blower or twin-screw supercharger. This component consists of two intermeshing helical rotors that draw in and compress air before delivering it to the engine’s intake manifold. The screw blower is typically mounted on top of the engine.

Working Principle and Mechanics of a Screw Blown Hemi

Air Induction: The process begins with the screw blower drawing in ambient air through its rotors. As the rotors turn, they trap air between them and compress it progressively.

Compressed Air Delivery: The compressed air is then forced into the engine’s intake manifold, where it mixes with fuel in the combustion chambers.

Combustion: The hemispherical combustion chambers of the Hemi engine ensure efficient combustion, promoting thorough air-fuel mixing. This results in a more potent and controlled combustion process.

Exhaust Expulsion: After combustion, exhaust gases are expelled through the exhaust valves and into the exhaust system.

Power Generation: The enhanced air-fuel mixture, combined with the high compression ratios characteristic of Hemi engines, results in exceptional power generation. This power is transmitted to the vehicle’s drivetrain, propelling the vehicle forward.

Factors Affecting the Design of a Screw Blown Hemi

Rotors and Screw Blower Design: The design of the screw blower’s rotors plays a critical role in determining the engine’s performance characteristics. Engineers carefully select rotor dimensions and configurations to optimize air compression and delivery.

Compression Ratio: The compression ratio of a Screw Blown Hemi engine is a key factor in its design. Engineers must balance the compression ratio with boost pressure to prevent detonation and ensure reliable operation.

Tuning and Fueling: Achieving optimal performance from a Screw Blown Hemi engine requires precise tuning of the engine’s fuel and ignition systems. Advanced engine management systems are often employed to achieve this level of control.

Tuning and Customization Options

Aftermarket Modifications: Enthusiasts and racing teams often turn to aftermarket modifications to further enhance the performance of Screw Blown Hemi engines. These can include custom tuning, upgraded supercharger components, and strengthened internals to handle the increased power.

Fuel Selection: The choice of fuel, whether conventional gasoline or high-octane racing fuels, can significantly impact the engine’s performance and power output. Tuning and calibration must be adjusted accordingly.

What Is A Screw Blown Hemi

Performance and Power Output of Screw Blown Hemi Engines

Screw Blown Hemi engines are celebrated for their extraordinary performance and power output, making them a dominant force in the world of high-performance and racing applications.

This section explores the factors that contribute to their exceptional performance and the records they have set in various automotive disciplines.

Comparison of Power Output Between Traditional Hemi Engines and Screw Blown Hemi Engines

Traditional Hemi Engines: Traditional Hemi engines, while powerful in their own right, typically produce power outputs in the range of several hundred to just over 700 horsepower in stock form.

These engines rely on the inherent advantages of the Hemi design, such as hemispherical combustion chambers, to achieve their performance.

Screw Blown Hemi Engines: In contrast, Screw Blown Hemi engines take the power potential to an entirely different level. These engines, equipped with screw blowers, are known for producing well over 1,000 horsepower, with some heavily modified variants exceeding 2,000 horsepower.

The integration of a screw blower significantly increases the engine’s air intake capacity, resulting in immense power gains.

Factors Contributing to Increased Performance

Forced Induction: The primary factor driving the increased power output of Screw Blown Hemi engines is the inclusion of a screw blower or twin-screw supercharger. These devices compress and deliver a significantly larger volume of air to the engine, enabling more substantial fuel combustion and power generation.

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High Compression Ratios: Screw Blown Hemi engines often feature high compression ratios, a characteristic shared with traditional Hemi engines. This high compression enhances the engine’s thermal efficiency and contributes to increased power.

Optimized Combustion: The Hemi architecture’s hemispherical combustion chambers promote efficient and thorough air-fuel mixing, resulting in cleaner and more potent combustion. This optimized combustion process further boosts power and torque.

Racing Applications and Records

Drag Racing: Screw Blown Hemi engines are highly coveted in drag racing due to their ability to deliver immediate, explosive power. They have set numerous records in quarter-mile runs, achieving incredible acceleration and top speeds.

Top Fuel and Funny Car: Screw Blown Hemi engines are commonly found in Top Fuel Dragsters and Funny Cars, the fastest vehicles in drag racing. These engines propel these machines to speeds exceeding 300 miles per hour in a matter of seconds.

Land Speed Racing: In land speed racing, where vehicles aim to set records for top speeds on salt flats or dry lakebeds, Screw Blown Hemi engines have propelled cars to astonishing velocities.

Custom and High-Performance Vehicles: Beyond racing, Screw Blown Hemi engines are utilized in custom and high-performance street cars, where they provide exhilarating acceleration and unmatched power.

Pros and Cons of Screw Blown Hemi Engines

Screw Blown Hemi engines are renowned for their exceptional performance and power output, but like any technology, they come with their set of advantages and disadvantages.

These pros and cons are crucial for evaluating their suitability for specific applications and their impact on the overall automotive experience.

Advantages of Screw Blown Hemi Engines

Exceptional Power Output: One of the primary advantages of Screw Blown Hemi engines is their unparalleled power output. They can generate well over 1,000 horsepower, making them a top choice for high-performance and racing applications where extreme power is desired.

Immediate Torque: The combination of a Screw Blown Hemi engine and a screw blower results in substantial low-end torque. This provides strong acceleration and responsiveness at lower RPM ranges, making them suitable for both drag racing and street use.

Proven Reliability: Well-engineered Screw Blown Hemi engines are known for their reliability, even in high-stress racing environments. Their robust design and durable components contribute to their reputation for longevity.

Customization Options: Enthusiasts and racing teams can fine-tune and customize Screw Blown Hemi engines to suit specific performance goals and applications. Aftermarket components and tuning options allow for flexibility in achieving desired power levels.

Potential Disadvantages and Challenges

Cost Considerations: The high-performance components and engineering required for Screw Blown Hemi engines can result in elevated production and maintenance costs. These engines are often more expensive to purchase and maintain than standard powerplants.

Fuel Efficiency: Achieving high power levels often comes at the expense of fuel efficiency. Screw Blown Hemi engines are known for their thirst for fuel, making them less economical in terms of fuel consumption compared to more efficient engines.

Emissions Concerns: As high-performance engines, Screw Blown Hemi engines may produce higher levels of emissions, potentially leading to environmental and regulatory challenges, especially in regions with stringent emissions standards.

Complexity: The integration of a screw blower adds complexity to the engine’s design and maintenance requirements. Ensuring proper calibration and maintenance of the supercharger system is essential for optimal performance and longevity.

Space Constraints: The physical size and design of Screw Blown Hemi engines may limit their applicability in some vehicle designs. Their larger dimensions can pose challenges for installation in compact or space-constrained engine bays.

FAQs About Screw Blown Hemi Engines

What is a Screw Blown Hemi engine?

A Screw Blown Hemi engine is a high-performance internal combustion engine known for its unique design and exceptional power output.

It combines a Hemi-style combustion chamber with a supercharger that employs twin-screw technology to force more air into the engine, resulting in increased horsepower and torque.

How does a Screw Blown Hemi differ from a traditional Hemi engine?

While both use Hemi-style combustion chambers (hemispherical), a Screw Blown Hemi incorporates a supercharger with twin-screw rotors to compress and force more air into the engine, significantly boosting its power and efficiency compared to a naturally aspirated Hemi engine.

What is the purpose of the supercharger in a Screw Blown Hemi engine?

The supercharger in a Screw Blown Hemi engine serves to compress and force a greater volume of air into the combustion chamber. This compressed air allows for more fuel to be burned, resulting in increased power and performance.

What are the advantages of a Screw Blown Hemi engine?

Increased horsepower and torque: The supercharger enhances air intake, leading to significantly higher power output.

Improved throttle response: Supercharging reduces lag, delivering power more quickly when you step on the gas.

Enhanced engine efficiency: The forced induction allows for better fuel-air mixture control, improving overall combustion efficiency.

Are Screw Blown Hemi engines used in everyday vehicles?

Screw Blown Hemi engines are typically reserved for high-performance and racing applications due to their extreme power output. They are less common in everyday passenger vehicles and more commonly found in drag racing cars, hot rods, and certain specialty vehicles.

How does the supercharger work in a Screw Blown Hemi engine?

The supercharger consists of twin-screw rotors that mesh together. As the rotors turn, they trap and compress air, forcing it into the engine’s intake manifold. This compressed air increases the engine’s air density, allowing it to burn more fuel and produce more power.

Can I retrofit my existing Hemi engine with a screw blower?

Yes, it is possible to retrofit an existing Hemi engine with a screw blower, but it can be a complex and expensive modification. It often involves substantial changes to the engine’s internals, fuel system, and exhaust, and it’s typically done by experienced engine builders or custom shops.

Are there different types of superchargers for Screw Blown Hemi engines?

Yes, there are various types of superchargers, including roots, twin-screw, and centrifugal. Screw Blown Hemi engines commonly use twin-screw superchargers because of their efficiency and ability to provide substantial low-end torque.

What are the maintenance requirements for a Screw Blown Hemi engine?

Maintaining a Screw Blown Hemi engine can be more demanding than a naturally aspirated engine due to the additional complexity of the supercharger. Regular maintenance includes checking and maintaining the supercharger, monitoring boost levels, and ensuring proper cooling to prevent overheating.

Are Screw Blown Hemi engines street legal?

In many places, Screw Blown Hemi engines are legal for street use, but specific regulations and emissions requirements may vary by location. It’s essential to check local laws and ensure that the engine meets all emissions and safety standards if you plan to use it on public roads.


In conclusion, a screw-blown Hemi represents a remarkable fusion of engineering prowess and high-performance automotive technology.

This specialized type of engine, born from the iconic Hemi legacy, takes power and efficiency to new heights by incorporating a screw-type supercharger into its design.

The result is a force of nature under the hood, capable of delivering breathtaking horsepower and torque figures, making it a favorite among drag racers and automotive enthusiasts alike.

As the automotive industry continues to evolve, the screw-blown Hemi stands as a testament to the relentless pursuit of speed and innovation, ensuring that the spirit of the Hemi engine lives on in the hearts of those who crave the ultimate in power and performance.






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