The 6.4L 392 HEMI represents Dodge's modern interpretation of American muscle - a naturally aspirated V8 that produces serious power while maintaining street drivability. Found in Scat Pack Chargers and Challengers, plus various other Mopar performance applications, this engine has become a favorite among enthusiasts looking for big displacement and even bigger power potential. At Raw Exotics, the 392 HEMI is one of our most frequently modified platforms, and I'm here to share everything you need to know about building these incredible engines.
392 HEMI Stock Specifications
Understanding what you're working with from the factory is crucial before planning modifications.
Engine Architecture and Design
The 392 HEMI (6.4L) shares its basic architecture with the smaller 5.7L HEMI but with significant upgrades for higher performance:
- Displacement: 392 cubic inches (6.4 liters)
- Bore x Stroke: 103.9mm x 94.6mm (4.09" x 3.72")
- Compression Ratio: 10.9:1
- Block Material: Cast aluminum with pressed-in iron liners
- Cylinder Heads: Aluminum with hemispherical combustion chambers
- Valvetrain: Overhead valve, hydraulic roller lifters, variable valve timing (VVT)
- Fuel System: Sequential multi-port fuel injection
Factory Power Output
Stock power varies slightly depending on application and model year:
- 2011-2014 SRT8 models: 470 HP @ 6,000 RPM, 470 lb-ft @ 4,200 RPM
- 2015+ Scat Pack models: 485 HP @ 6,100 RPM, 475 lb-ft @ 4,100 RPM
- Challenger/Charger Widebody (2020+): 485 HP, 475 lb-ft
What's impressive about the 392 is the broad, usable powerband. Peak torque arrives early and stays strong through redline, making these engines incredibly responsive on the street.
Key Internal Components
The 392 uses robust internals from the factory:
- Pistons: Cast aluminum, eutectic construction
- Connecting Rods: Forged powdered metal, capable of handling significant power
- Crankshaft: Forged steel, fully counterweighted
- Camshaft: Hydraulic roller, relatively aggressive profile for a factory cam
These components are stronger than many enthusiasts realize, which is why the 392 can handle substantial power increases with bolt-ons alone.
Stage 1: Bolt-On Modifications (500-550 HP)
The 392 responds incredibly well to basic bolt-on modifications. Here's how to wake up your HEMI without opening the engine.
Cold Air Intake: 8-15 HP
The factory airbox is restrictive, particularly at higher RPM. A quality cold air intake frees up airflow and improves throttle response.
Recommended intakes:
- Arrington Performance Cold Air Intake: Proven gains, excellent build quality
- K&N Typhoon CAI: Good value, easy installation
- S&B Filters Cold Air Intake: Designed specifically for Mopar applications
Expect 8-12 HP with the intake alone, 12-15 HP when combined with a tune. More importantly, throttle response improves significantly.
Headers and Exhaust: 20-35 HP
This is where 392s make serious naturally aspirated gains. The factory exhaust manifolds and restrictive cats choke power significantly.
Long-Tube Headers:
Premium options include American Racing Headers (ARH), Kooks, and Stainless Works. Long-tubes provide maximum gains:
- 20-25 HP from headers alone
- 30-35 HP when combined with tune
- Improved exhaust note and aggressive sound
- Requires ECU tuning to prevent check engine lights
Mid-Pipe and Cat-Back:
Combine headers with a high-flow mid-pipe and cat-back exhaust from Corsa, Borla, or MagnaFlow for maximum flow. Complete exhaust system with tune nets 30-40 HP total.
ECU Tuning: 25-40 HP
Proper ECU calibration is essential to unlock the 392's full potential. Even on a stock engine, tuning provides significant gains.
What tuning changes:
- Ignition timing optimization (factory is conservative)
- Air/fuel ratio adjustments for maximum power
- Variable valve timing refinement
- Throttle response enhancement
- Transmission tuning for better shift points and firmness
- Speed limiter removal
We use several tuning platforms at Raw Exotics:
- HP Tuners: Our primary choice for comprehensive custom tuning
- DiabloSport inTune: Good pre-loaded tunes with some customization
- Arrington Performance: Excellent Mopar-specific calibrations
A quality tune on an otherwise stock 392 adds 25-30 HP. With supporting mods (intake, headers, exhaust), expect 35-45 additional horsepower.
Throttle Body Upgrade: 8-12 HP
The stock 85mm throttle body becomes restrictive as power increases. Upgrading to a 90-92mm throttle body from Arrington Performance or Modern Muscle eliminates this bottleneck.
Gains are modest on otherwise stock engines but increase with other modifications. Budget $400-600 for quality units.
Typical Stage 1 Results
Combining intake, headers, exhaust, throttle body, and professional tuning typically yields:
- Peak power: 530-550 HP (crank), 450-475 WHP
- Torque: 510-530 lb-ft
- Quarter-mile: Low 12s @ 115-118 MPH (in a Charger/Challenger)
- Cost: $3,500-5,000 total
- Reliability: Excellent - stock internals handle this easily
Stage 2: Heads and Cam (580-620 HP)
For enthusiasts chasing naturally aspirated power beyond 550 HP, cylinder head and camshaft upgrades are the next step.
Camshaft Selection
The 392's factory cam is decent but conservative. Aftermarket cams significantly improve airflow and shift the powerband higher.
Popular camshaft options:
Arrington Performance Cams:
- Stage 1 cam (street friendly): 550-580 HP, maintains drivability
- Stage 2 cam (aggressive street): 580-610 HP, choppy idle but streetable
- Stage 3 cam (race): 610-650 HP, requires race fuel, compromised street manners
Comp Cams HEMI Cam Kits:
- Proven performance, extensive R&D
- Good customer support and technical resources
- Various profiles for different applications
Texas Speed HEMI Cam:
- Excellent value for the performance
- Well-suited for street/strip builds
- Good idle quality for the power level
Cylinder Head Work
The factory 392 heads flow quite well, but there's room for improvement:
- CNC porting: Precision port work extracts maximum airflow (30-40 HP gain)
- Valve upgrades: Larger stainless steel valves improve flow
- Spring upgrades: Necessary when installing aggressive camshafts
- Multi-angle valve job: Improves sealing and flow characteristics
Expect $1,500-2,500 for quality head work. Some builders opt for aftermarket heads like those from Arrington or Mast Motorsports for ultimate flow ($4,000-6,000 per pair).
Supporting Modifications for Cam Swaps
Camshaft upgrades require additional components:
- Upgraded valve springs (prevent valve float)
- Chromoly pushrods (stronger than stock)
- Quality lifters (hydraulic roller or solid roller for race applications)
- Timing chain and gear set
- ARP head studs (recommended for reliability)
Heads/Cam Package Results
Typical results from heads and cam package with supporting bolt-ons:
- Peak power: 580-620 HP (crank), 500-530 WHP
- Torque: 540-570 lb-ft
- RPM range: Power peak shifts to 6,500-6,800 RPM (vs 6,100 stock)
- Quarter-mile: High 11s @ 120-123 MPH
- Cost: $5,000-8,000 (parts and labor)
- Drivability: Moderate cam maintains street manners; aggressive cams sacrifice idle quality
Forced Induction: Superchargers and Turbos
While naturally aspirated 392 builds are impressive, forced induction is where these engines truly dominate. The 392's large displacement and strong internals make it perfect for boost.
Supercharger Systems
Supercharging is the most popular forced induction option for 392 HEMIs due to instant throttle response and linear power delivery.
Whipple 2.9L Supercharger:
- Most popular kit, proven reliability
- 700-750 HP on pump gas (93 octane)
- 800-850 HP on E85 or race gas
- Complete kit includes supercharger, intercooler, fuel system, and all hardware
- Cost: $8,500-9,500
- Excellent street manners with proper tuning
ProCharger P-1SC or F-1X:
- Centrifugal supercharger (different power delivery than Whipple)
- P-1SC: 650-700 HP on pump gas
- F-1X: 750-850 HP on pump gas
- Less heat than positive displacement superchargers
- Top-end power emphasis (less low-end torque than Whipple)
- Cost: $7,000-8,500
Magnuson TVS2300:
- Roots-style positive displacement supercharger
- 650-700 HP on pump gas
- Instant throttle response
- Often includes warranty options
- Cost: $7,500-8,500
Turbocharger Systems
Twin-turbo setups are less common on 392s due to packaging challenges and higher cost, but they offer massive power potential.
Quality twin-turbo kits from STS Turbo or custom fabrication:
- 800-900 HP with conservative boost (6-8 psi)
- 1,000-1,200 HP with higher boost and built motor
- Better thermal efficiency than superchargers
- More complex installation
- Cost: $10,000-15,000+ depending on components
Supporting Mods for Forced Induction
Boosted 392s require additional upgrades:
Fuel System (700+ HP):
- High-flow fuel pump (DeatschWerks, Aeromotive)
- Upgraded fuel injectors (60+ lb/hr for 700 HP, 80+ lb/hr for 800+ HP)
- Potentially dual fuel pump setup for extreme builds
Cooling System:
- Upgraded intercooler (for centrifugal superchargers)
- Heat exchanger upgrade (for positive displacement superchargers)
- Auxiliary oil cooler for sustained high-power use
Transmission and Driveline:
- 8HP70/8HP90 automatic transmission can handle ~650 lb-ft stock
- Transmission tune to raise torque limits
- Upgraded clutch packs for 700+ HP applications
- Upgraded rear axle shafts and differential for serious power
Built Motor: Maximum Power
Stock 392 internals are surprisingly strong, but there are limits. For ultimate power and reliability, internal upgrades become necessary.
Stock Internal Limits
Based on our experience at Raw Exotics:
- Peak safe power on stock internals: 750-800 HP / 650-700 lb-ft
- Factors affecting reliability: Tuning quality, fuel quality, detonation control
- Common failure points: Pistons (cracking under sustained detonation), rod bolts
Forged Internal Upgrade
For 800+ HP applications, we recommend forged internals:
- Forged pistons: JE, Wiseco, or Mahle, designed for boost with appropriate ring gaps
- Forged connecting rods: Manley H-beam or Oliver rods rated for 1,200+ HP
- Crankshaft: Stock crank is forged and adequate to 1,000 HP; upgrade to billet for extreme builds
- Main studs and rod bolts: ARP hardware throughout
- Bearings: Quality bearings from King, Clevite, or ACL
Built motor cost: $12,000-18,000 for complete forged bottom end with assembly and machine work
Power Potential with Built Motor
- Street build (93 octane): 900-1,000 HP
- E85 build: 1,000-1,200 HP
- Race gas build: 1,200-1,500 HP
- All-out racing (methanol, extreme boost): 1,500+ HP possible
Common 392 HEMI Issues
While generally reliable, 392s have a few known issues:
Lifter Failure
Some 392s experience hydraulic lifter failure, causing ticking noises and eventual cam lobe wear. This is more common in earlier production years (2011-2014).
Prevention:
- Use quality synthetic oil (0W-40 or 5W-40)
- Regular oil changes (every 5,000 miles)
- Avoid extended idling when possible
- Consider aftermarket lifters when doing cam swaps
Spark Plug Fouling
Rich running conditions or oil consumption can foul spark plugs. Regular inspection and replacement prevents misfires.
Recommendations:
- Use OEM-spec spark plugs (NGK or Champion)
- Replace every 30,000 miles (more frequently with mods)
- Check for proper air/fuel ratios if frequent fouling occurs
Throttle Body Issues
Electronic throttle body can develop carbon buildup or sensor issues, causing rough idle or reduced power.
Solution: Periodic throttle body cleaning and ECU relearning procedure
Real-World Power Levels and Costs
Here's a realistic breakdown of power levels and associated costs:
Stock: 485 HP / 475 lb-ft, $0
Bolt-Ons (Stage 1): 530-550 HP / 510-530 lb-ft, $3,500-5,000
Heads/Cam (Stage 2): 580-620 HP / 540-570 lb-ft, $8,000-12,000 total
Supercharged (Stock Motor): 700-850 HP / 650-750 lb-ft, $12,000-16,000 total
Built Motor + Blower: 900-1,200 HP / 800-1,000 lb-ft, $30,000-45,000 total
Final Thoughts
The 6.4L 392 HEMI is an exceptional platform for performance enthusiasts. Whether you're looking for a mild street cruiser with 550 HP or an all-out drag car pushing 1,000+ horsepower, the 392 can deliver. Its large displacement, strong factory internals, and excellent aftermarket support make it one of the best modern V8 engines for modification.
"There's something special about HEMI power. The 392 combines old-school displacement with modern technology - it's the best of both worlds. And when you hear that supercharger whine on top of a HEMI rumble, you know you've built something special." - Josh Munford
At Raw Exotics, we've built everything from bolt-on 392s to full race engines exceeding 1,200 HP. No matter your goals or budget, we can help you extract maximum performance from your HEMI. Stop by our Houston shop and let's discuss your 392 build - whether you want simple bolt-ons or a complete built motor, we have the experience and passion to make it happen.