What a 6.4-liter Engine Really Means

A 6.4-liter engine refers to the engine’s displacement—the total volume swept by all pistons inside the cylinders—as the pistons move from top to bottom. In practical terms, it means the engine displaces 6.4 liters of air-fuel mixture per full cycle (6,400 cubic centimeters), roughly equivalent to 392 cubic inches. It does not describe oil capacity, fuel tank size, or guaranteed horsepower.

Definition and Context

Engine displacement is a fundamental specification that quantifies how much air-fuel mixture an engine can draw in during one complete cycle across all cylinders. Automakers express it in liters (L) or cubic centimeters (cc) globally and in cubic inches (cu in) in some U.S. contexts. A 6.4-liter engine sits on the larger end of passenger-vehicle engines and is common in performance cars and heavy-duty trucks where strong low- to mid-range torque is prized.

How Displacement Is Calculated

Displacement is the sum of the swept volumes of each cylinder. For a single cylinder, volume equals the area of the cylinder bore multiplied by the stroke (the distance the piston travels). Total engine displacement equals that single-cylinder volume multiplied by the number of cylinders. This is why two engines with different cylinder counts can share the same displacement if their bore and stroke dimensions lead to the same combined volume.

Key Conversions and Notes

Because engine sizes are often cross-referenced across measurement systems, it helps to anchor the numbers: 6.4 liters equals 6,400 cc and is approximately 390.6 to 392 cubic inches (manufacturers often round to “392”). While the badge may say 6.4L, the true figure can be slightly more or less due to rounding or marketing conventions.

What Displacement Does—and Doesn’t—Tell You

The following points outline what a 6.4-liter rating indicates about an engine and what it does not guarantee. This helps avoid common misunderstandings when comparing vehicles or reading spec sheets.

• Does indicate: the total swept volume of all cylinders (air-fuel mixture capacity per cycle).
• Does indicate: a general tendency toward higher torque at lower rpm compared with smaller-displacement engines, all else equal.
• Does indicate: potential for greater fuel consumption and emissions compared with smaller engines under similar operating conditions.
• Does not indicate: exact horsepower or torque—those depend on tuning, aspiration (naturally aspirated vs. turbo/supercharged), compression ratio, cam profiles, fueling, and exhaust design.
• Does not indicate: engine’s physical size, weight, or number of cylinders (a 6.4L could be a V8 or, less commonly, other configurations).
• Does not indicate: oil capacity, coolant capacity, or fuel tank size.

In short, displacement is a useful starting point for understanding an engine’s character, especially its torque potential, but it should be considered alongside design and technology choices that drive actual performance and efficiency.

Real-World Implications

Large-displacement engines like a 6.4L typically deliver strong, accessible torque, suiting towing, hauling, and performance driving. The trade-offs often include higher fuel consumption and greater CO2 output, which can affect operating costs and, in some regions, taxes or insurance. Modern powertrains sometimes match or surpass large-displacement torque with smaller, turbocharged engines, but the response and sound characteristics differ, and heavy-duty applications still frequently rely on larger displacements for durability and sustained load capability.

Examples of 6.4-Liter Engines in the Market

To ground the concept, here are well-known engines that carry a 6.4-liter designation across different vehicle types and eras.

• Stellantis (Chrysler/Dodge/Ram) 6.4L HEMI V8: Branded as “392,” used in performance models like the Dodge Challenger/Charger Scat Pack and in Ram heavy-duty trucks, tuned for either high output or durability depending on application.
• Ford 6.4L Power Stroke V8 Diesel (2008–2010): A turbocharged diesel used in F-Series Super Duty trucks, illustrating that “6.4L” can also describe diesel displacement, not just gasoline engines.
• Aftermarket and racing builds: Custom 6.4L configurations appear in motorsports and tuning communities, where bore and stroke are adjusted to hit a target displacement for class rules or performance goals.

These examples show that the same displacement can span gasoline and diesel technologies, with wide variance in power, torque, and usage depending on engineering and tuning.

Common Misconceptions

Many shoppers confuse displacement with other capacities or assume it dictates performance. The distinctions below can prevent costly assumptions.

• Not oil capacity: An engine labeled 6.4L might only hold around 6–8 quarts of oil (varies by model), not 6.4 liters of oil.
• Not a power guarantee: A modern 3.0L twin-turbo engine can match or exceed the horsepower of some naturally aspirated 6.4L engines, though their torque curves and driving feel may differ.
• Not always about cylinder count: Displacement doesn’t specify whether it’s a V8, V10, etc.—only the total swept volume.

Keeping these differences in mind helps interpret engine badges and spec sheets accurately, especially when cross-shopping modern turbocharged engines against larger naturally aspirated ones.

Bottom Line

“6.4 liter” is a measurement of engine displacement—the total volume swept by all pistons—and a broad indicator of the engine’s torque-oriented character and likely fuel use. It’s a meaningful but incomplete metric: true performance and efficiency depend on the engine’s overall design, aspiration, and calibration.

Summary

A 6.4-liter engine displaces 6,400 cc (about 392 cu in) across all cylinders, representing the volume of air-fuel mixture it can process each cycle. While larger displacement often correlates with stronger low-end torque and a brawny driving feel, it doesn’t dictate horsepower, efficiency, or cylinder count. Consider displacement alongside the engine’s technology and tuning to understand how a vehicle will perform and behave in the real world.

What does liter size in an engine mean?

In the context of an engine, “liter” (L) refers to engine displacement, which is the total volume of all the cylinders combined. A 2.0L engine, for example, means its total cylinder volume is 2.0 liters. This volume represents the amount of air and fuel the engine can burn during a combustion cycle. A larger displacement generally indicates a more powerful engine because it can burn more fuel and air to create a bigger “bang”.
 
How Displacement is Calculated

• A liter is a unit of volume, equivalent to 1,000 cubic centimeters (cc). 
• Engine displacement is the sum of the volume of each cylinder, measured from the top of the cylinder to the bottom as the piston moves. 
• So, a 2.0L engine is the same as a 2,000cc engine. 

Why Displacement Matters

• Power & Performance: Opens in new tabA larger displacement means a greater capacity to burn fuel and air, which translates to more horsepower and torque. 
• Fuel Economy: Opens in new tabHistorically, larger displacement engines had worse fuel economy, but modern technologies like turbocharging and direct injection allow smaller engines to be more powerful and efficient. 
• Vehicle Applications: Opens in new tabSmaller engines (e.g., 1.0–2.5L) are common in fuel-efficient compact cars, while larger engines (e.g., 4.0L and up) are found in SUVs and trucks where power is a priority. 

Important Considerations

• Technology: Modern advancements, such as turbocharging, can make a smaller, turbocharged engine more powerful than a larger, naturally aspirated engine. 
• Engine Type: Engine liters do not indicate the engine’s type (e.g., petrol, diesel, hybrid, or electric). 
• Overall Design: Factors like the engine’s design, number of cylinders, and other components also significantly influence its overall power and performance. 

Is a 6.4 liter engine good?

The 6.4L HEMI is generally a robust engine, especially when used within its intended parameters. Regular maintenance and using recommended materials can help prevent many common issues, ensuring longevity and performance.

Are the 5.7 and 6.4 the same block?

No, the 5.7L HEMI and 6.4L HEMI (also known as the 392) do not use the same engine block. The 6.4L engine uses a stronger, thicker block, referred to as a Big Gas Engine (BGE) block, designed for higher performance and a better foundation for modifications compared to the 5.7L block.
 
This video explains the differences between the 5.7L and 6.4L HEMI engines: 59sMopar MotorsportsYouTube · Jan 21, 2022
Here are the key differences:

• Block Design: The 6.4L HEMI is built on the more robust BGE block, while the 5.7L HEMI has a less robust block. 
• Strength for Modifications: The 6.4L’s stronger block is better suited for handling higher power output from modifications like forced induction. 
• Performance: The 6.4L offers significantly more horsepower and torque from the factory, partly due to its larger displacement and reinforced engine components. 
• Components: While some components are shared (like throttle bodies), the blocks and internal components are distinct to handle the increased power and stresses of the 6.4L. 

Is a 6.4 liter a V8?

6.4L HEMI® V8 ENGINE. With TorqueFlite® 8 eight-speed automatic transmission.