The .7 HEMI engine is a legendary powerplant, known for its robust architecture and immense tuning potential. With the right combination of parts and careful tuning, hitting 600+ horsepower is not just a pipe dream—it's a repeatable, documented milestone. This guide walks through the essential modifications, focusing on the Mopar Stage 3 Camshaft and Edelbrock Intake Manifold, along with supporting upgrades needed to safely and reliably reach that target.

Understanding the .7 HEMI Engine Family

The ".7 HEMI" typically refers to the third-generation HEMI V8 engines displacing 6.1L, 6.2L (Hellcat), or 6.4L (392/BGE). These engines share the hemispherical combustion chamber design that promotes efficient airflow and combustion, but the 6.4L (392) is the most common platform for building 600+ naturally aspirated horsepower. It features a forged steel crank, powdered metal rods, and aluminum pistons from the factory, along with high-flow cylinder heads. Understanding the specific engine you are working with—whether it's a 6.1L, 6.4L, or a 6.2L Hellcat variant—is critical because each has different stock components, compression ratios, and rev limits.

For a naturally aspirated 6.4L, reaching 600 horsepower at the crank requires a roughly 100+ hp gain over stock, which is aggressive but achievable with a proper cam, intake, headers, and tuning. The 6.2L Hellcat engine is already supercharged and can easily exceed 600 hp with pulley and tune, but this guide focuses on naturally aspirated builds where the cam and intake deliver the biggest gains.

Key Components for 600+ HP

To reach 600+ horsepower in a .7 HEMI, you need to treat the engine as a system. The camshaft and intake manifold are the main drivers, but they won't deliver their full potential without supporting mods. Here is the core list of required components:

  • Mopar Stage 3 Camshaft (or equivalent aftermarket cam)
  • Edelbrock Performer RPM or Victor II Intake Manifold
  • High-flow cylinder heads (optional but recommended for max gains)
  • High-performance fuel injectors (at least 60 lb/hr or larger)
  • Long-tube headers with high-flow exhaust
  • Cold air intake
  • Professional ECU tuning (dyno tuning essential)

Each of these parts must be matched to the engine's airflow capacity. For example, a Stage 3 cam with 0.650" lift and high duration demands an intake manifold that can flow at high RPMs without choking the top end.

Mopar Stage 3 Camshaft: The Heart of the Build

The Mopar Stage 3 Camshaft (part number P5155875 for 6.4L) is an official Mopar Performance part designed to maximize airflow in the 6.4L HEMI. It features approximately 0.650" intake lift, 0.650" exhaust lift, with 280+ degrees of advertised duration on both lobes. This aggressive profile moves the powerband up significantly, shifting peak horsepower to the 6,200–6,500 RPM range. It is a direct-fit hydraulic roller cam that uses the factory lifters and timing chain, though many builders upgrade to a heavy-duty timing chain at this power level.

Benefits of the Stage 3 Cam

  • +40–60 rear-wheel horsepower over stock, depending on supporting mods.
  • Shorter intake and exhaust duration compared to full race cams, retaining decent drivability with a proper tune.
  • Pronounced idle lope that gives the engine an aggressive sound, indistinguishable from a full race prepped HEMI.
  • Optimized for high-flow cylinder heads; if you keep stock heads, the cam will still work but may not reach the full 600+ hp target without porting.

However, this cam requires upgraded valve springs because the factory springs cannot handle the higher lift and ramp rates. Mopar offers a valve spring upgrade kit (part number P5249755) that is essential for reliability above 6,000 RPM. Installing a cam is a major job—it requires removing the front engine cover, timing chain, and phaser, so many owners opt for a professional install.

Edelbrock Intake Manifold: Breathing Room

Edelbrock offers several intake manifolds for the .7 HEMI, but the two best options for a 600+ hp naturally aspirated build are the Performer RPM 5.7/6.1/6.4 and the Victory Jr. Single Plane (now known as the Edelbrock Victor II). For street/strip applications, the Performer RPM is the more common choice because it preserves low- and mid-range torque while greatly improving top-end flow. The Victor II is a single-plane design that sacrifices some low-end drivability for peak top-end horsepower—ideal if the car will see significant track time.

Features of the Edelbrock Performer RPM for HEMI

  • Dual-plane design with 100% increased plenum volume over the stock 6.4L intake.
  • Flows approximately 1,000+ CFM, enough to support 600+ hp with a cam and headers.
  • Works with stock throttle body but benefits from upgrading to a 90mm or 92mm throttle body for maximum airflow.
  • Runners are longer and larger to match the cam's higher RPM powerband.

When pairing the Edelbrock intake with the Mopar Stage 3 cam, expect solid torque gains from 2,500 RPM upward, with the most significant gains above 4,500 RPM. The intake alone can add 25–35 horsepower on a 6.4L HEMI with a tune.

Supporting Modifications for the 600+ HP Target

Simply bolting on a cam and intake will not get you to 600+ hp—you need to address the engine's fuel, exhaust, and ignition systems. Below are the critical supporting upgrades required to safely make that power.

High-Performance Fuel Injectors

The stock 6.4L HEMI fuel injectors are about 33 lb/hr (at 58 psi), which is sufficient for the stock 485 hp rating. At 600+ hp, you'll need at least 60 lb/hr injectors to maintain proper fuel delivery and duty cycle. Many builders choose 80 or 100 lb/hr injectors to leave headroom for future upgrades (like nitrous) and to run E85, which requires roughly 30% more fuel volume. A modern injector like the Fuel Injector Connection 80 lb/hr injectors works well and is compatible with the stock fuel rail.

High-Flow Exhaust System

Long-tube headers are a must for any 600+ hp HEMI build. Stock exhaust manifolds are restrictive and will choke the engine's top end. Headers like American Racing Headers or Kooks offer stepped primaries that improve exhaust scavenging. Pair headers with a full 3-inch or 3.5-inch exhaust system with an X- or H-pipe, and free-flowing mufflers. The exhaust backpressure must be minimized to allow the cam's long-duration exhaust lobes to evacuate gases efficiently.

Cold Air Intake and Throttle Body

A quality cold air intake (CAI) reduces inlet air temperature and improves flow capacity. On a 6.4L, a CAI alone can add 10–15 hp. Upgrading to a 90mm or 92mm throttle body (such as the BDC Performance billet throttle body) will reduce the pressure drop across the throttle plate and complement the Edelbrock intake. The stock 86mm throttle body is a choking point once the cam and intake are upgraded.

ECU Tuning: The Make-or-Break Element

After all parts are installed, the engine control unit (ECU) must be calibrated to the new hardware. A professional dyno tune using HP Tuners or DiabloSport inTune is essential. The tuner will adjust fuel maps, ignition timing, idle speed, and transmission shift points (if automatic) to match the cam's powerband. Without a tune, the engine will run lean, knock, and likely misfire, causing serious damage. Tuning can yield an additional 20–30 horsepower on top of the parts, by optimizing the air/fuel ratio and spark advance for 91–93 octane fuel.

A common issue with the Mopar Stage 3 cam is a low-vacuum idle that can cause the ECU to stall or set codes. The tuner will need to adjust the idle air control and set a higher idle RPM (typically 850–900 RPM) to maintain a stable idle. Many tuners also disable MDS (cylinder deactivation) if the car has it, because the cam's aggressive lobes do not work well with the variable displacement system.

Achieving 600+ Horsepower: A Proven Recipe

To quantify the build, here is a realistic power output expectation using the described components on a 6.4L HEMI:

  • Stock 6.4L HEMI (485 hp at crank): baseline
  • + Mopar Stage 3 Cam + valve springs + install: +50–60 hp
  • + Edelbrock Performer RPM intake + 92mm throttle body: +30–40 hp
  • + Long-tube headers + 3-inch exhaust: +25–35 hp
  • + Cold air intake + tuning: +15–25 hp
  • Total: 605–645 crank horsepower (approximately 520–550 rear-wheel horsepower on a chassis dyno).

This formula has been proven by many Mopar enthusiasts and shops. Achieving 600+ hp at the wheels (700+ at the crank) would typically require ported cylinder heads, a larger cam, and possibly a stroker kit. But for a street-driven car that still passes emissions (depending on state) and is reliable, the cam/intake combination is the sweet spot.

Common Pitfalls and Considerations

Valvetrain Stability

With the Mopar Stage 3 cam's 0.650" lift, valve float becomes a concern above 6,500 RPM. Upgrading to dual valve springs (Mopar P5249755 or aftermarket like Comp Cams 26926) is non-negotiable. Additionally, consider upgrading to chromoly pushrods and steel roller rockers if the engine will see sustained high RPM use. Some builders also replace the timing chain with a heavy-duty double-roller chain and a billet cam gear.

Oil System

The .7 HEMI uses a dual oiling system with a crank-driven oil pump. At high RPM, the stock oil pan baffling can cause oil starvation during hard cornering. Installing a windage tray or a high-capacity oil pan (like the Moroso 20525) is recommended for track use. Some builders also add an oil accumulator (Accusump) for added safety.

Drivetrain Upgrades

600+ hp will overwhelm a stock drivetrain in most applications. The 6-speed manual (TR-6060) can handle the power, but the clutch must be upgraded to a twin-disc or triple-disc unit. For automatics, the 8HP70 transmission used in newer Chargers/Challengers can be tuned to survive 600 hp, but the torque converter should be restalled to match the cam's powerband (typically 2,500–3,000 RPM stall). Rear axles and differential carriers may also need upgrading if the car is a daily driver that sees drag strip abuse.

Conclusion

The .7 HEMI engine is a robust platform that responds exceptionally well to cam and intake upgrades. By using the Mopar Stage 3 Camshaft and Edelbrock Performer RPM intake manifold, along with properly chosen supporting modifications—fuel injectors, headers, cold air intake, and professional tuning—600+ naturally aspirated horsepower is a well-documented achievement. This combination delivers a thrilling driving experience with improved throttle response, a menacing idle, and substantial top-end pull. For those who want more, the sky is the limit; but for a reliable, streetable 600+ hp package, this recipe delivers without compromise.