Ever wondered what makes a Hemi engine truly special? When it comes to pure American muscle, few powerplants command as much respect as the 6.4 Hemi. This modern marvel combines old-school displacement with cutting-edge technology to deliver the kind of performance that turns heads and pins you to your seat.
Whether you’re considering a vehicle equipped with this powerhouse or just admiring from afar, you’ll want to know what makes it tick. Let’s dive into everything that matters about the 6.4 Hemi engine specs and see why it’s become such a legend in the performance world.
What Is a 6.4 Hemi Engine?
The 6.4 Hemi (also known as the 392 Hemi) is Chrysler’s large-displacement V8 engine that serves as the heart of many high-performance Dodge, Jeep, and Ram vehicles. Introduced in 2011, this naturally-aspirated powerplant was designed to replace the earlier 6.1L Hemi in SRT vehicles.
“392” refers to the engine’s displacement in cubic inches, connecting it to Chrysler’s heritage. The original 392 Hemi from the late 1950s shared this displacement figure, though the modern version is completely redesigned with today’s technology.
What makes it a “Hemi”? The name comes from its hemispherical combustion chambers that allow for larger valves and better airflow. This design promotes more complete combustion and higher performance than traditional combustion chamber designs.
6.4 Hemi Engine Specifications
Let’s break down the key specifications that make this engine truly special:
Displacement and Dimensions
The 6.4L Hemi has a displacement of exactly 6,417cc (392 cubic inches). This hefty size is achieved through:
- Bore: 103.9mm (4.09 inches)
- Stroke: 94.5mm (3.72 inches)
- Block Type: Cast iron with deep-skirt design
- Cylinder Configuration: 90-degree V8
These dimensions create an optimal balance between torque production and high-RPM capability, allowing the engine to deliver impressive power across a broad RPM range.
Power Output
The 6.4 Hemi’s output varies slightly depending on application:
| Application | Horsepower | Torque | RPM Range |
|---|---|---|---|
| SRT Cars (2015+) | 485 hp | 475 lb-ft | 6,100/4,200 RPM |
| SRT Cars (2011-2014) | 470 hp | 470 lb-ft | 6,000/4,200 RPM |
| Jeep/Dodge SUVs | 475 hp | 470 lb-ft | 6,000/4,300 RPM |
| Ram Trucks | 366-410 hp | 429 lb-ft | 5,600/4,000 RPM |
The differences in output stem from varying intake designs, exhaust systems, and engine management tuning based on the vehicle’s intended use.
Internal Components
The 6.4 Hemi uses premium internal components designed for performance and durability:
- Crankshaft: Forged steel for maximum strength
- Connecting Rods: High-strength powder metal
- Pistons: Hypereutectic aluminum with flat-top design
- Compression Ratio: 10.9:1 (cars/SUVs) or 10.0:1 (trucks)
- Redline: 6,400 RPM
These robust internals allow the engine to handle substantial power increases beyond factory specifications when modified, making it popular with enthusiasts.
Valvetrain and Breathing
The 6.4 Hemi’s breathing capabilities are central to its impressive performance:
Valvetrain Specifications
- Valve Arrangement: 16 valves (2 per cylinder)
- Ignition: 16 spark plugs (2 per cylinder)
- Intake Valve Diameter: 54.3mm
- Exhaust Valve Diameter: 42mm
- Intake Valve Lift: 15.0mm (0.591 inches)
- Exhaust Valve Lift: 14.0mm (0.551 inches)
- Camshaft Material: Nodular iron
Induction System
The intake system varies by application:
- Performance Cars: Short-runner plastic intake manifold optimized for high-RPM power
- Trucks: Active dual-runner intake manifold for better low-end torque
Both systems utilize Sequential Multi-Port Electronic Fuel Injection, delivering precisely metered fuel for optimal combustion across all operating conditions.
Performance and Real-World Capabilities
The 6.4 Hemi transforms vehicles into genuine performers. Here’s what it delivers in the real world:
Acceleration Performance
When installed in performance-oriented models like the Dodge Charger SRT 392, the engine enables:
- 0-60 MPH: Low 4-second range
- Top Speed: 182 MPH
- Quarter Mile: Mid-12 second range
These impressive figures put 6.4 Hemi-powered vehicles in genuine sports car territory despite their often larger size and higher weight.
Driving Characteristics
The 6.4 Hemi delivers a distinctive driving experience characterized by:
- Immediate throttle response
- Linear power delivery throughout the RPM range
- Muscular exhaust note
- Surprising flexibility for daily driving
Unlike smaller turbocharged engines, the 6.4 Hemi’s naturally-aspirated design provides instant response without turbo lag, creating a more connected driving experience.
Vehicle Applications
The 6.4 Hemi has powered an impressive variety of vehicles since its introduction:
Performance Cars
- Dodge Challenger SRT 392
- Dodge Charger SRT 392
SUVs
- Jeep Grand Cherokee SRT
- Dodge Durango SRT
Trucks
- Ram 2500/3500 pickup trucks
- Ram 3500/4500/5500 chassis cab models
Each application features specific calibrations to optimize the engine for its intended use, whether that’s track performance, towing capability, or off-road adventure.
Reliability and Durability
The 6.4 Hemi is built for both performance and longevity:
Durability Features
- Piston Cooling Jets: Spray oil onto the underside of pistons to manage heat
- Oil-to-Water Oil Cooler: Standard equipment for thermal management
- Cross-Bolted Main Caps: Provide exceptional crankshaft stability
- Deep-Skirt Block Design: Enhances rigidity and reduces noise/vibration
Maintenance Considerations
Owners should be aware of these maintenance factors:
- Fuel Recommendation: Premium fuel (91+ octane) is recommended, especially for high-performance applications
- Oil Capacity: Approximately 7 quarts with filter
- Oil Type: Full synthetic 0W-40 oil is typically recommended
- Interval: Factory-recommended oil change intervals are around 8,000-10,000 miles, but many enthusiasts change more frequently
With proper maintenance, these engines have proven to be reliable power plants capable of high mileage operation.
Engineering Innovations
Several technical innovations help the 6.4 Hemi deliver its impressive performance:
Multi-Displacement System (MDS)
In truck applications, the 6.4 Hemi uses Chrysler’s MDS technology to deactivate four cylinders under light load conditions, improving fuel economy. The system seamlessly transitions between V8 and V4 modes with minimal driver awareness.
Fuel Saver Technology
The engine employs advanced electronic throttle control and variable valve timing to optimize fuel delivery and combustion efficiency across various operating conditions.
Thermal Management
The 6.4 Hemi uses sophisticated thermal management systems including:
- Active grille shutters on some applications to manage airflow
- Variable-speed cooling fans
- Dual thermostats for more precise temperature control
These systems help maintain optimal operating temperatures for both performance and efficiency.
Comparison to Key Competitors
How does the 6.4 Hemi stack up against its rivals in the performance V8 segment?
| Engine | Displacement | Horsepower | Torque | Notable Features |
|---|---|---|---|---|
| 6.4 Hemi | 6.4L (392ci) | 485 hp | 475 lb-ft | Hemispherical chambers, dual ignition |
| Ford 5.0 Coyote | 5.0L (302ci) | 460-480 hp | 420-430 lb-ft | DOHC, 32-valve design |
| Chevy LT1 | 6.2L (376ci) | 455-490 hp | 455-465 lb-ft | Direct injection, variable valve timing |
The 6.4 Hemi offers the largest displacement of the three, with competitive output figures despite using a more traditional OHV (pushrod) valvetrain design versus the DOHC setups of some competitors.
Modifying the 6.4 Hemi
The 6.4 Hemi has become a favorite for modification, with substantial power increases possible through various upgrades:
Common Modifications
- Cold Air Intake: Often the first modification, typically adding 10-15 horsepower
- Headers and Exhaust: Long-tube headers and less restrictive exhaust can add 20-30 horsepower
- Camshaft Upgrade: More aggressive camshafts can add 40-70 horsepower depending on specifications
- Cylinder Head Modifications: Ported and polished heads improve airflow for additional power
- Supercharger Kits: Adding forced induction can boost output to 600-700+ horsepower
The robust internals of the 6.4 Hemi make it capable of handling significant additional power with proper supporting modifications and tuning.
Historical Context
The 6.4 Hemi carries forward a storied heritage dating back to the original Chrysler Hemi engines:
- First Generation (1951-1958): The original “FirePower” Hemi engines, including the first 392ci version
- Second Generation (1964-1971): The legendary 426 “Elephant” Hemi that dominated NASCAR and drag racing
- Third Generation (2003-present): Modern Hemi engines including the 5.7L, 6.1L, 6.4L, and supercharged 6.2L variants
The current 6.4L was developed under the code name “Apache,” paying homage to its historical predecessor while incorporating modern technology for emissions compliance, reliability, and drivability that would have been unimaginable in the muscle car era.
The Future of the 6.4 Hemi
As automotive technology evolves toward electrification, the naturally aspirated 6.4 Hemi represents something of a high-water mark for traditional V8 engines. While its long-term future remains uncertain in an increasingly electrified world, it continues to develop a passionate following among enthusiasts who appreciate its combination of old-school character and modern capability.
For now, the 6.4 Hemi remains in production, continuing to power some of America’s most exciting performance vehicles and capable trucks. Its legacy as one of the great modern American V8 engines is already secure, regardless of what the future holds.
Final Thoughts on the 6.4 Hemi
The 6.4 Hemi stands as a remarkable achievement in modern engine design – a powerplant that delivers impressive performance while maintaining the character and sound that muscle car enthusiasts crave. With its robust construction, generous displacement, and thoughtful engineering, it delivers a driving experience that’s increasingly rare in today’s automotive landscape.
Whether powering a tire-smoking Challenger, a track-capable Jeep, or a hard-working Ram truck, the 6.4 Hemi provides a perfect blend of brute force and sophisticated engineering that continues to win fans among those who appreciate authentic American performance.
