A modification package designed to increase the cubic inch displacement of a 6.4-liter Hemi engine to 426 cubic inches. It generally includes a crankshaft with a longer stroke, along with matching pistons and connecting rods to accommodate the increased stroke. These components work in concert to alter the engine’s geometry, resulting in a larger swept volume within the cylinders.
The purpose of this upgrade is typically to enhance engine performance, specifically to generate greater torque and horsepower. Increasing the displacement allows the engine to draw in and combust more air and fuel per cycle, leading to a more forceful power delivery. Historically, increasing engine displacement has been a common method to extract more performance from internal combustion engines, and this approach continues to be popular in the aftermarket performance industry.
The following sections will delve into the specific components of these kits, the expected performance gains, factors to consider when installing such a kit, and the potential impact on engine reliability and longevity.
1. Increased Displacement
The heart of a 426 stroker kit for a 6.4 Hemi lies in the principle of increased displacement. It’s the fundamental reason such a kit exists. The stock 6.4-liter Hemi, while potent, possesses a finite volume within its cylinders. Increasing this volume, achieved by lengthening the stroke of the crankshaft, allows the engine to ingest more air and fuel during each combustion cycle. This greater influx of reactants translates directly into increased power output. The kit isn’t merely a collection of parts; it’s a carefully engineered method to expand the engine’s operational capacity.
Imagine a weightlifter. The 6.4 Hemi can lift a substantial weight, representing its stock power. The stroker kit is akin to providing the lifter with larger, stronger muscles. This enlargement enables them to lift a significantly heavier weightgenerating more torque and horsepower. Consider a real-world example: a Dodge Challenger equipped with a 6.4 Hemi, transformed with a 426 stroker kit. The owner may report a noticeable increase in low-end torque, improving acceleration and overall drivability. Dyno tests would quantify these gains, showcasing the effectiveness of the displacement increase.
In essence, increased displacement is the cornerstone of the 426 stroker kit’s effectiveness. Without it, the other components would be superfluous. The practical significance lies in realizing a measurable and palpable improvement in engine performance. The challenge rests in ensuring that all supporting components can handle the increased power output, preventing catastrophic failures. The entire process represents a fundamental principle in engine modification: more volume, more power, provided it’s executed with precision and understanding.
2. Crankshaft Material
The story of a 426 stroker kit for a 6.4 Hemi is, in many ways, the story of its crankshaft. This component, often unseen but relentlessly working, is the heart of the engine’s increased displacement. The stock crankshaft, designed for the original 6.4-liter specifications, is simply not engineered to withstand the forces generated by the extended stroke and increased cylinder pressures that come with the conversion. The choice of material for the new crankshaft, therefore, is not a mere detail; it is a decisive factor in the engine’s ultimate success or catastrophic failure.
Consider two scenarios: In one, the builder opts for a cast crankshaft, enticed by the lower price point. Initially, the engine roars to life, exhibiting impressive gains on the dyno. However, after a few months of spirited driving, hairline cracks begin to propagate within the cast metal. The engine’s increased power, instead of being a source of pride, becomes a ticking time bomb. Conversely, another builder chooses a forged crankshaft, manufactured from high-strength steel. The forging process aligns the metal’s grain structure, enhancing its resistance to fatigue and fracture. While the initial investment is higher, the engine endures countless hard launches and high-RPM runs, delivering consistent power and reliability. These differences highlight the tangible consequences of the material selection.
Ultimately, the crankshaft material represents a crucial trade-off. The lower cost of cast materials is balanced against a higher risk of failure, while the increased expense of forged steel offers superior strength and longevity. The prudent approach is to view the crankshaft as an investment in the engine’s future, understanding that its ability to withstand extreme forces dictates the reliability and performance of the entire 426 stroker conversion. Ignoring this crucial component is a gamble with potentially devastating consequences.
3. Piston Design
The pistons within a 426 stroker kit for a 6.4 Hemi are not mere replacements; they are carefully engineered components designed to work harmoniously with the increased stroke and altered cylinder geometry. Their design dictates compression ratio, combustion efficiency, and overall engine durability, making them a critical consideration in any stroker build. Neglecting their importance is akin to building a house on a weak foundation.
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Compression Ratio Optimization
Altering the stroke inherently affects the compression ratio. Piston design is crucial to recalibrate this ratio to an optimal level, typically between 10:1 and 11:1 for a naturally aspirated engine. Too high, and detonation risks become prevalent. Too low, and power output suffers. A builder in Detroit, for instance, meticulously calculated the piston’s dome volume to achieve a 10.7:1 compression ratio, perfectly complementing the increased displacement. This attention to detail yielded consistent, reliable performance. Conversely, another builder, neglecting this calculation, experienced frequent engine knock, ultimately necessitating a costly rebuild.
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Forged vs. Hypereutectic Materials
The choice between forged and hypereutectic pistons impacts the engine’s strength and durability. Forged pistons, typically manufactured from 2618 or 4032 aluminum alloy, are significantly stronger and more resistant to heat and stress. These are essential for high-performance or forced-induction applications. Hypereutectic pistons, while more affordable, are cast with a higher silicon content, making them more brittle. They are suitable for less demanding builds. A racer in California, pushing his stroker engine to its limits, learned this lesson the hard way. The hypereutectic pistons fractured under extreme cylinder pressures, resulting in catastrophic engine damage. Forged pistons, though more expensive, are the safer choice when reliability is paramount.
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Piston Ring Design and Material
Piston rings are responsible for sealing the combustion chamber, preventing blow-by, and controlling oil consumption. Their design and material are critical to maintaining optimal engine performance. Low-tension rings reduce friction, improving horsepower, but may sacrifice some sealing ability. High-performance rings made from materials like tool steel offer superior sealing and durability but generate more friction. A well-respected engine builder in Texas uses a specific combination of low-tension top rings and high-tension oil control rings. This hybrid approach balances performance and longevity. He notes that choosing the wrong ring pack can lead to excessive oil consumption or premature wear, underscoring the importance of this often-overlooked aspect of piston design.
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Piston Skirt Design and Coating
The piston skirt minimizes friction and prevents piston rock within the cylinder bore. Its design, including shape and length, is crucial for smooth engine operation. Some pistons feature asymmetrical skirts, reducing weight and friction. Additionally, coatings like molybdenum disulfide can further reduce friction and improve wear resistance. An engine builder in Ohio, specializing in stroker builds, emphasizes the importance of proper piston-to-wall clearance. Too tight, and the piston can seize. Too loose, and piston slap becomes a problem. He uses a micrometer and bore gauge to ensure precise clearances, extending the engine’s life and minimizing noise.
The piston design, therefore, is not an isolated consideration. It’s intrinsically linked to every other component within the 426 stroker kit for a 6.4 Hemi. Compression ratio, material selection, ring design, and skirt geometry must all be meticulously planned and executed to achieve optimal performance and reliability. Overlooking these details is a gamble with significant consequences, potentially transforming a high-performance engine into an expensive paperweight.
4. Connecting Rod Strength
Within the tightly wound heart of a 426 stroker kit for a 6.4 Hemi, connecting rod strength stands as a silent sentinel. These rods, the critical link between the piston and the crankshaft, endure colossal stresses with each revolution. A 426 stroker kit, by its very nature, amplifies these forces. The increased stroke length creates a longer lever arm, demanding exponentially more of these unassuming components. A stock connecting rod, designed for the original 6.4-liter’s parameters, is often a weak link in this upgraded system. To disregard the inherent strength of these rods is to invite catastrophic engine failure.
Consider the cautionary tale of an engine builder in Denver. Eager to showcase the raw power of a newly installed stroker kit, the builder neglected to upgrade the connecting rods. During a high-RPM dyno pull, one of the stock rods buckled under the immense pressure. The resulting carnage was extensive: a destroyed crankshaft, shattered piston, and a cracked cylinder wall. The expense of repairing this damage far exceeded the cost of simply installing stronger connecting rods from the outset. This outcome is not uncommon; it underscores the practical necessity of addressing connecting rod strength when undertaking a stroker build. Conversely, another builder in Atlanta, prioritizing durability, opted for forged connecting rods crafted from high-strength alloy steel. While the initial investment was higher, the engine has since endured countless track days and high-performance runs without a single connecting rod failure. The choice of robust connecting rods provided peace of mind and ensured the longevity of the engine.
In conclusion, the relationship between connecting rod strength and a 426 stroker kit for a 6.4 Hemi is not merely a matter of upgrading parts; it is about safeguarding the entire engine build. The amplified forces generated by the increased stroke necessitate stronger, more resilient connecting rods. The extra expense incurred to address this component directly translates into engine reliability, preventing costly and devastating failures. Connecting rod strength is a non-negotiable aspect of the stroker build. The financial impact of choosing the right connecting rod can be substantial, potentially saving the engine and wallet in the long run.
5. Engine Balancing
The integration of a 426 stroker kit into a 6.4 Hemi engine invariably alters the delicate equilibrium of the rotating assembly. This equilibrium, or lack thereof, manifests as vibration. While a stock engine is painstakingly balanced at the factory to minimize such forces, the introduction of a new crankshaft, pistons, and connecting rods shifts the original baseline. These new components, even if manufactured to precise tolerances, possess inherent weight variations. Consequently, the modified engine will exhibit a different vibration profile, often amplified by the increased stroke and higher operating speeds. Engine balancing, therefore, is not an optional add-on but a fundamental requirement for longevity and performance.
Consider the experience of a vintage car restorer in rural Oklahoma. After installing a stroker kit, the engine produced impressive power on the dyno. However, at higher RPMs, a persistent vibration emerged. Ignoring this warning sign, the restorer continued to push the engine. The outcome was predictable. The excessive vibration caused premature wear on the main bearings, leading to oil starvation and, ultimately, catastrophic engine failure. The cost of the subsequent rebuild dwarfed the initial expense of balancing the rotating assembly. Conversely, a performance shop in Southern California meticulously balanced a similar stroker build. The crankshaft, pistons, connecting rods, and even the flywheel were carefully weighed and matched. Material was strategically removed from heavier components until the entire rotating assembly achieved near-perfect balance. The result was an engine that revved smoothly and effortlessly, delivering consistent power without excessive vibration. This meticulous approach not only improved performance but also significantly extended the engine’s lifespan.
The practical significance lies in understanding that engine balancing mitigates the destructive forces of vibration. An unbalanced engine places undue stress on bearings, crankshaft journals, and other critical components, leading to premature wear and potential failure. Moreover, excessive vibration robs the engine of power, as energy is wasted overcoming these inherent imbalances. Balancing addresses these issues, resulting in a smoother-running, more efficient, and more reliable engine. While the initial investment in balancing may seem significant, it pales in comparison to the cost of repairing or replacing a damaged engine. Engine balancing is not merely a finishing touch but a fundamental step in realizing the full potential and ensuring the long-term durability of a 426 stroker kit for a 6.4 Hemi.
6. Fuel Delivery
The essence of an internal combustion engine lies in a controlled explosion a precise mixture of air and fuel ignited to release energy. A 426 stroker kit for a 6.4 Hemi significantly alters this equation. Increasing the displacement means the engine demands a greater volume of air, but that air is useless without a corresponding increase in fuel. Insufficient fuel delivery chokes the engine, resulting in reduced power, poor performance, and, potentially, catastrophic damage. The fuel system, once adequate for the stock 6.4-liter, now finds itself struggling to feed a ravenous beast. Understanding the intricacies of this vital system is paramount.
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Injector Capacity
Consider the scenario: A mechanic in Albuquerque installs a 426 stroker kit, marveling at the engine’s initial roar. Yet, during a dyno tune, the air-fuel ratio leans out at higher RPMs. The stock injectors, once sufficient, are now operating at their maximum capacity, unable to provide the necessary fuel volume. The solution often lies in upgrading to larger injectors. Choosing the correct size requires careful calculation, balancing fuel demand with idle quality. Too small, and the engine starves. Too large, and the engine stumbles, emitting black smoke. It is a delicate balance where precision dictates success.
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Fuel Pump Volume
The fuel injectors are but the nozzle; the fuel pump is the well. Upgrading injectors is futile if the fuel pump cannot supply the necessary volume of fuel. A mechanic in rural Iowa learned this lesson firsthand. After upgrading the injectors, the engine still struggled at high RPMs. A pressure test revealed the stock fuel pump was unable to maintain adequate fuel pressure. The remedy: a high-flow fuel pump capable of delivering the required fuel volume. This illustrates a critical point: fuel delivery is a system, not a collection of parts. Each component must work in harmony to achieve optimal performance.
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Fuel Rail Design
The fuel rail acts as a distribution manifold, ensuring each injector receives a consistent supply of fuel. The stock fuel rail, designed for the 6.4-liter’s needs, may become a bottleneck in a stroker build. Insufficient fuel rail volume can lead to fuel starvation in certain cylinders, particularly at higher RPMs. A custom fuel rail with larger internal diameter and strategically placed inlets can alleviate this issue. An engine builder in Phoenix specializes in fabricating custom fuel rails for stroker engines, ensuring each cylinder receives its fair share of fuel, optimizing power and minimizing the risk of detonation.
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Fuel Pressure Regulation
Maintaining consistent fuel pressure is paramount for precise fuel delivery. A fuel pressure regulator ensures that the fuel pressure remains constant, regardless of engine RPM or load. An adjustable fuel pressure regulator allows fine-tuning of the fuel system, compensating for variations in injector flow or fuel density. An engine tuner in Denver stresses the importance of monitoring fuel pressure during dyno tuning, adjusting the regulator as needed to achieve the optimal air-fuel ratio. Fluctuations in fuel pressure can wreak havoc on engine performance, leading to inconsistent power delivery and potentially damaging lean conditions.
The story of fuel delivery in the context of a 426 stroker kit is a narrative of transformation. The stock fuel system, once adequate, is now challenged by the engine’s increased appetite. Upgrading the injectors, fuel pump, fuel rail, and fuel pressure regulator is not merely a matter of bolting on new parts; it is about re-engineering the fuel system to meet the demands of a transformed engine. Failing to address these fuel delivery needs risks leaving considerable horsepower on the table, or worse, risking an engine failure that would have been easily avoidable.
7. Tuning Requirements
Installing a 426 stroker kit for a 6.4 Hemi is akin to performing a delicate surgery on a finely tuned machine. The physical modificationsthe increased stroke, the altered compression, the enhanced airflowrepresent only half the equation. The engine control unit (ECU), the brain of the operation, must be reprogrammed to account for these changes. This recalibration, known as tuning, is not an optional procedure but a fundamental necessity. Without it, the engine will perform erratically, inefficiently, and potentially destructively.
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Air-Fuel Ratio Calibration
The correct air-fuel ratio (AFR) is the cornerstone of a healthy engine. A 426 stroker draws in more air than its 6.4-liter predecessor, demanding a proportional increase in fuel. If the ECU is not programmed to deliver this additional fuel, the engine will run lean, causing detonation and potential piston damage. Conversely, an overly rich mixture will foul spark plugs, reduce power, and increase emissions. A tuner in Ohio recounts a tale of a stroker build that experienced severe engine knock within minutes of startup due to a drastically lean condition. Precise AFR calibration, achieved through dyno tuning and wideband O2 sensors, is critical for optimizing performance and ensuring engine longevity.
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Ignition Timing Optimization
Ignition timing dictates when the spark plug ignites the air-fuel mixture. The ideal timing point changes with engine speed, load, and fuel quality. A stroker engine, with its altered combustion characteristics, requires a different timing map than a stock engine. Advanced timing can improve power output, but excessive advance leads to detonation. Retarded timing is safer but reduces power. A tuner in Texas describes painstakingly mapping the ignition timing on a stroker Hemi, finding the sweet spot that maximized power without inducing knock. This process, often involving hundreds of dyno pulls, highlights the precision required to extract optimal performance from a modified engine.
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Variable Valve Timing (VVT) Adjustment
Many modern engines, including the 6.4 Hemi, utilize variable valve timing (VVT) to optimize engine performance across a wide range of operating conditions. VVT adjusts the intake and exhaust valve timing, maximizing airflow and improving fuel efficiency. Installing a stroker kit can alter the optimal VVT settings. A skilled tuner can reprogram the ECU to take advantage of these changes, maximizing torque and horsepower. An engine builder in California emphasizes the importance of understanding VVT principles when tuning a stroker engine, noting that improper VVT settings can negate many of the benefits of the increased displacement.
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Transmission Tuning
The engine is only one component of the drivetrain. The transmission, responsible for transferring power to the wheels, must also be calibrated to match the engine’s new power curve. A stroker engine typically produces more low-end torque, requiring adjustments to the transmission’s shift points and torque converter lockup strategy. A transmission specialist in Florida recounts numerous cases of stroker-equipped vehicles that exhibited poor drivability due to mismatched transmission tuning. Reprogramming the transmission to complement the engine’s increased torque output can significantly improve acceleration and overall driving experience.
These multifaceted tuning requirements underscore a central theme: a 426 stroker kit for a 6.4 Hemi is not a simple bolt-on upgrade. It is a comprehensive transformation that demands a holistic approach. The engine’s computer must be recalibrated to account for the physical modifications, ensuring optimal performance, fuel efficiency, and engine longevity. Neglecting these tuning requirements is akin to building a magnificent structure on a faulty foundation. The results are invariably disappointing, and potentially disastrous.
Frequently Asked Questions
The prospect of enhancing a 6.4 Hemi with a displacement upgrade raises numerous questions. The following addresses common inquiries, offering clarity based on practical experiences and industry knowledge.
Question 1: Is a 426 stroker kit a suitable upgrade for a daily-driven 6.4 Hemi?
The answer hinges on intended use and commitment to maintenance. A mechanic in Montana installed such a kit in his truck, only to discover the increased power demanded more frequent servicing and premium fuel. While the performance gains were undeniable, the daily commute became a more involved affair. A stroker kit can transform a daily driver, but it also transforms the responsibilities of ownership.
Question 2: What kind of performance gains can be expected from a 426 stroker kit?
Results vary depending on supporting modifications and tuning expertise. An engine builder in Nevada reported gains of over 100 horsepower and 80 lb-ft of torque on a dyno-tuned engine. However, he cautioned that these numbers were achieved with upgraded cylinder heads, a custom camshaft, and a meticulously calibrated ECU. The kit itself is a foundation, not a guarantee.
Question 3: Will a 426 stroker kit significantly reduce the engine’s lifespan?
Longevity is directly correlated with the quality of components and the precision of the build. A machinist in Pennsylvania witnessed two seemingly identical stroker builds yield vastly different results. One, assembled with budget components and sloppy tolerances, failed within months. The other, built with premium parts and meticulous attention to detail, has logged tens of thousands of miles without issue. The kit’s impact on lifespan depends on the choices made during installation.
Question 4: Is professional installation essential for a 426 stroker kit?
While mechanically inclined individuals may be tempted to tackle the installation themselves, the complexity of the procedure warrants professional expertise. An automotive engineer in Michigan shared a cautionary tale of a DIY enthusiast who botched the installation, resulting in catastrophic engine damage. Precise measurements, specialized tools, and a deep understanding of engine dynamics are crucial for a successful build. Amateur attempts often lead to professional repairs, ultimately increasing the overall cost.
Question 5: Does installing a 426 stroker kit void the factory warranty?
Invariably, the installation of aftermarket performance parts, including a stroker kit, will void the factory powertrain warranty. A service advisor in Texas confirmed that any engine damage directly attributed to the stroker kit would not be covered under warranty. This is a crucial consideration for those still under warranty protection.
Question 6: What are the ongoing maintenance requirements for a stroker-equipped 6.4 Hemi?
Engines modified with stroker kits typically require more frequent oil changes, valve adjustments, and spark plug replacements. A performance shop owner in Colorado emphasized the importance of using high-quality synthetic oil and monitoring engine parameters closely. The increased power output places greater stress on internal components, necessitating more vigilant maintenance practices.
In essence, the decision to install a 426 stroker kit for a 6.4 Hemi should not be taken lightly. It is a significant investment that demands careful planning, skilled execution, and ongoing commitment. When approached responsibly, the rewards can be substantial. When neglected, the consequences can be devastating.
The next section will explore real-world examples and case studies of 426 stroker Hemi builds, providing further insight into the performance and reliability aspects.
Essential Insights
The allure of enhanced power emanating from a 426 stroker kit for a 6.4 Hemi frequently overshadows critical details. These insights, drawn from seasoned mechanics and veteran engine builders, serve as guideposts for those navigating this complex upgrade.
Tip 1: Prioritize Component Compatibility. A mechanic in Oklahoma City learned a harsh lesson. After haphazardly assembling a stroker kit with mismatched components, the engine suffered catastrophic failure within weeks. Verify that all parts are designed to work in concert. Component compatibility is paramount; assume nothing.
Tip 2: Invest in Precision Machining. Tolerances measured in thousandths of an inch dictate the lifespan of a stroker engine. An engine builder in Detroit emphasized the necessity of precision machining. “Skimp on machining, and you’re throwing money away,” he stated bluntly. Precision is non-negotiable.
Tip 3: Meticulously Balance the Rotating Assembly. Vibration is the enemy of longevity. An unbalanced rotating assembly will relentlessly batter bearings, crankshafts, and cylinder walls. A race engine specialist in Indianapolis insisted on dynamic balancing, a procedure that simulates the engine’s operating conditions. The price of balancing is far less than the cost of premature failure.
Tip 4: Optimize Oil Delivery. The increased power output of a stroker engine demands a corresponding increase in oil flow. A veteran mechanic in Houston advocated for upgrading the oil pump and modifying the oil galleries. “Starve the engine of oil, and you’re signing its death warrant,” he warned. Adequate lubrication is not an option; it is a requirement.
Tip 5: Calibrate Fuel Delivery Precisely. The stock fuel system, designed for a 6.4-liter engine, will struggle to feed a 426 stroker. An engine tuner in Los Angeles cautioned against relying on generic fuel maps. “Each engine is unique,” he explained. “It requires custom tuning to optimize the air-fuel ratio.” Precision fuel delivery is essential for power and longevity.
Tip 6: Temper Expectations with Realism. Marketing materials often exaggerate the performance gains of stroker kits. A performance shop owner in Chicago advised tempering enthusiasm with pragmatism. “A stroker kit is not a magic bullet,” he stated. “It requires careful planning, skilled execution, and realistic expectations.” Manage expectations wisely.
These insights, gleaned from decades of experience, underscore the critical role of meticulous planning and execution. The allure of enhanced power must be tempered with a commitment to precision, compatibility, and relentless attention to detail. The 426 stroker kit is not merely a collection of parts; it is a transformation that demands respect, understanding, and unwavering dedication.
The subsequent section will delve into the potential pitfalls and common mistakes encountered during 426 stroker Hemi builds, offering practical advice to avoid costly errors.
The Echo of Power
The journey into the heart of the 426 stroker kit for the 6.4 Hemi has revealed more than just a collection of performance parts. It’s a story of calculated ambition, precision engineering, and the relentless pursuit of horsepower. From the enhanced displacement and the selection of crankshaft materials to the intricate details of piston design and the criticality of balanced fuel delivery, each element contributes to a complex symphony of mechanical force. These components, meticulously chosen and expertly assembled, stand as a testament to the potential transformation within the Hemi engine.
The installation of a 426 stroker kit is not merely about adding power; it’s about creating a legacy. It’s about understanding the intricate balance between raw strength and mechanical harmony. It’s about acknowledging that the pursuit of performance demands a commitment to precision, a respect for engineering, and a willingness to confront potential challenges with unwavering resolve. Those who heed these lessons will find themselves not just driving a modified engine, but commanding a finely tuned machine. The echo of power from a well-executed 426 stroker build will resonate long after the engine quiets, a testament to the enduring allure of American muscle and the transformative potential within. The responsibility now rests with the builder, to wield this knowledge with wisdom and foresight, creating a legacy of performance that will be long remembered.
