The 6.4-liter Hemi V8 has been a staple of modern American muscle, delivering power and torque straight from the factory. However, for enthusiasts who crave more than the stock 485 horsepower, building a forged-internals engine with a DiabloSport tuner unlocks a new level of performance. This article provides a comprehensive cost breakdown for such a build, covering parts, labor, supporting modifications, and the expected return on investment. Whether you’re planning a daily driver capable of 600+ horsepower or a dedicated strip car, understanding the financial outlay is critical.

The 6.4 Hemi Charger – A Solid Foundation for a Build

Before diving into costs, it’s important to appreciate the platform. The 2015–2023 Dodge Charger SRT 392 and Scat Pack models come equipped with the 6.4-liter (392 cubic inch) Hemi. Stock, the engine produces 485 horsepower and 475 lb‑ft of torque, thanks to forged connecting rods, variable cam timing, and a compression ratio of 10.9:1. The block is robust, but the pistons and rods are not designed for sustained power beyond roughly 600–650 horsepower, especially when forced induction or nitrous is added. That’s where forged internals and a DiabloSport tuner come into play, enabling reliable high-horsepower operation without compromising engine life.

Component Breakdown and Costs

Below is a detailed, line-item breakdown of the major expenses. Prices reflect current market averages (2024–2025) for quality aftermarket parts. Actual figures may vary based on vendor, sales, and regional labor rates.

DiabloSport Tuner and Custom Tuning

The DiabloSport i3 handheld tuner (part number DMU‑7295) is the entry point for recalibrating the factory ECU. It allows you to read/clear diagnostic codes, log performance data, and install custom tunes. For a forged build you will need a professional dyno tune or a remote custom tune from a reputable calibration shop.

  • DiabloSport i3 Tuner (new): $399 – $499
  • DiabloSport i3 Tuner (used in good condition): $250 – $350
  • Custom tune from a trusted calibrator (e.g., Hemifever, Modern Muscle Performance): $350 – $500
  • Dyno tuning session (if dyno tuning is chosen): $500 – $800 (typically 2–3 hours)

Total for tuning: $750 – $1,300 depending on route. Many owners opt for a remote tune via email to save money, then dyno confirm later. External resource: DiabloSport official site for current list pricing and supported vehicles.

Forged Internals – The Backbone of High Power

Forged components replace factory cast parts to withstand cylinder pressures exceeding 1,000 horsepower. For a 6.4 Hemi, the three core internal upgrades are pistons, connecting rods, and the crankshaft.

Forged Pistons

Forged pistons from brands such as Diamond, CP‑Carillo, or Manley are made of 2618 aluminum alloy for superior fatigue resistance. For a forced‑induction or high‑compression build, expect to pay:

  • Set of 8 forged pistons (with piston rings and wrist pins): $700 – $1,200
  • Piston ring set only (if reusing existing pistons, not recommended): $50 – $100
  • Factory piston replacement (cast), not advised for build: $400 – $600

Forged Connecting Rods

Forged steel rods (e.g., Oliver, K1 Technologies, or Manley H‑beam) handle higher RPM and boost levels. Stock 6.4 rods are cast and can fail around 700 lb‑ft of torque.

  • Set of 8 forged H‑beam connecting rods: $600 – $1,000
  • Rod bearings and assembly hardware: $100 – $200

Forged Crankshaft

The stock 6.4 crankshaft is cast nodular iron, adequate for moderate power increases. For serious builds (800+ hp) a forged billet or callout crankshaft (e.g., from R&E Racing or Bryant Racing) is recommended.

  • Forged crankshaft (callout, billet, or cast-steel upgrade): $1,500 – $2,500
  • Stock crankshaft (reused with proper machining): $0 (if kept, but may require balancing)

Total for forged internals (parts only): $2,800 – $4,900 depending on choices. The most common budget build uses forged pistons and rods while retaining the stock crank, as many have seen 800 whp on the factory crankshaft without issue.

Supporting Modifications

Forged internals and a tune demand upgrades to fuel, induction, and cooling systems to realize their potential safely.

Fuel System Upgrades

The factory fuel injectors and fuel pump are maxed around 550 whp. For builds targeting 600+ whp, upgrade to:

  • High‑flow fuel injectors (8x 80–100 lb/hr, e.g., FIC or Injector Dynamics): $400 – $600
  • In‑tank 525 lph fuel pump (e.g., Walbro or AEM): $250 – $400
  • Fuel pump wiring harness and voltage booster: $50 – $150
  • Ethanol content sensor if running E85: $100 – $200

Fuel system subtotal: $800 – $1,350

Exhaust System

To reduce backpressure and improve spool (if forced induction), a cat‑back or full exhaust is common. The factory exhaust is restrictive past 500 hp.

  • Cat‑back exhaust (Magnaflow, Borla, Corsa): $800 – $1,500
  • Long‑tube headers (American Racing, Kooks): $800 – $1,200
  • Mid‑pipes or off‑road downpipes: $200 – $400
  • Installation labor for headers (4–6 hours at $100–$150/hr): $400 – $900

Exhaust subtotal (parts + labor): $2,200 – $4,000

Cooling System

Increased power generates more heat. Upgrading the radiator, oil cooler, and adding a transmission cooler is wise for sustained runs.

  • High‑performance aluminum radiator (e.g., Mishimoto, C&R): $400 – $700
  • Electric cooling fans and controller: $200 – $400
  • Oil cooler upgrade (setrab or Mocal): $300 – $500
  • Transmission cooler (if automatic): $150 – $300
  • Installation labor: $200 – $400

Cooling subtotal: $1,250 – $2,300

Additional Considerations

Many builders also address the intake, valve train, and drivetrain.

  • Cold air intake system: $300 – $600
  • Throttle body (90mm+): $200 – $400
  • Valve springs (for high‑RPM builds): $150 – $300
  • Lifters and pushrods (if upgrading camshaft): $400 – $800
  • Camshaft (stage 2 or 3, often chosen with forged internals): $300 – $600
  • Transmission torque converter (for automatic): $500 – $1,000
  • Rear end upgrades (driveshaft, axles): $800 – $2,000

These additions quickly add $2,500 – $5,700 to the total. Consider them based on your target horsepower.

Labor and Installation Costs

Unless you have engine building experience, professional labor is a major expense. A full forged‑internals short‑block assembly typically costs:

  • Engine removal and disassembly: $800 – $1,500
  • Machine work (bore, hone, deck, balance, line honing): $600 – $1,200
  • Short‑block assembly with forged internals: $1,000 – $2,000
  • Installation of long‑block, sensors, and accessories: $1,200 – $2,500
  • Dyno tuning session (if not remote): $500 – $800
  • Total labor for a turnkey build: $4,100 – $8,000+

Many shops offer package deals. For a fully assembled, drop‑in forged 6.4 short‑block (pistons, rods, crank, bearings, gaskets, and machine work) you might pay $4,500 – $6,500 for parts and labor combined.

Total Estimated Cost and Budgeting

Let’s compile two realistic scenarios: a budget build (550–650 whp) and an all‑out build (700–900 whp).

Budget Build (550–650 whp, pump gas or E85)

  • DiabloSport tuner + custom remote tune: $750
  • Forged pistons + rods (retain stock crank): $1,600
  • Machine work + assembly (labor): $1,500
  • Supporting mods: Fuel pump + injectors + exhaust (no headers) + cold air: $2,500
  • Clutch/transmission upgrade (if manual, consider a new clutch): $500
  • Misc (gaskets, fluids, bolts): $300
  • Total: ~$7,150

All‑Out Build (700–900 whp, E85, headers, cam, cooling)

  • DiabloSport tuner + dyno tune: $1,100
  • Full forged internals (pistons, rods, billet crank): $4,500
  • Full machine work + assembly: $2,500
  • Supporting mods: Fuel system, exhaust, headers, cam, cooling, intake, drivetrain: $6,000
  • Transmission upgrade (built 8HP70 or clutch): $2,000
  • Labor for full engine pull + install + tuning: $3,500
  • Misc: $500
  • Total: ~$20,100

These estimates align with real forum reports on LXForums and Hellcat.org. External resource: LXForums build threads for firsthand cost tracking.

Expected Performance Gains

A forged 6.4 Hemi with a good tune and minimal supporting mods (intake, headers, exhaust) typically produces 520–560 whp on 93 octane, and up to 620–680 whp on E85. Adding a cam and ported heads can push to 600+ whp on pump gas and near 700 whp on ethanol. With forced induction (centrifugal or twin‑screw supercharger), forged internals are necessary to exceed 700 whp reliably, and 800–900 whp is achievable with the right fuel and tuning.

For context, a stock Scat Pack Charger dynos around 410–430 whp. So a budget build adds roughly 100–150 whp, while an all‑out naturally aspirated build can add 200+ whp. That translates to quarter‑mile times in the low 11s to high 10s with drag radial tires.

Final Thoughts and Recommendations

Building a forged‑internal 6.4 Hemi Charger with a DiabloSport tuner is a serious financial commitment, but it offers immense satisfaction and capability. The key is to define your horsepower goal early, because it dictates every cost. For a street‑car that sees occasional track use, the budget build (around $7,000 in parts and labor) is a smart investment—reliable, fast, and well‑documented. For a dedicated race car or showstopper, the all‑out build at $20,000+ delivers legendary power but demands rigorous maintenance and drivetrain upgrades.

Before starting, get multiple quotes from reputable engine builders and tuners who specialize in the 6.4 Hemi. Websites like MotorTrend and Hemi Build offer valuable build guides. Always factor in a 10–15% contingency for unforeseen parts and labor. With careful planning, your 6.4 Charger can become a reliable pavement‑wrecking machine that rivals much more expensive platforms.