The .4 HEMI cam swap is one of the most rewarding modifications you can make to a 5.7L, 6.1L, or 6.4L HEMI engine. Enthusiasts have documented gains of 50 rear-wheel horsepower (RWHP) or more with a properly selected camshaft and supporting modifications. While the process requires mechanical skill, patience, and the right tools, this expanded step-by-step guide will walk you through every phase – from selecting the ideal cam to dialing in the ECU tune. By the end, you will understand not just how to perform the swap, but also how to avoid common pitfalls and maximize your power gains.

Understanding the Benefits of a Cam Swap

Before lifting a wrench, it is critical to understand exactly what a camshaft swap does for a .4 HEMI engine. The factory camshaft is designed for a balance of fuel economy, emissions compliance, and smooth idle. A performance camshaft alters valve timing, lift, and duration to improve airflow through the engine. This directly translates to higher peak horsepower and torque, particularly in the mid-to-upper RPM range. Real-world dyno results from shops like American Racing Headers often show 50–80 RWHP gains on a 6.4L HEMI with a cam swap, headers, and a tune.

  • Increased Power: Aggressive lobe profiles allow more air and fuel into the cylinders, increasing volumetric efficiency. Expect peak RWHP gains of 40–70 on a 5.7L and 60–90 on a 6.4L with proper supporting mods.
  • Improved Throttle Response: A performance cam can sharpen throttle response by reducing overlap and improving low-lift flow, though this depends on the specific grind.
  • Enhanced Exhaust Note: The lope at idle is one of the most satisfying side effects. The idle quality will become more aggressive, giving your car or truck a distinct muscular tone.
  • Broadened Power Band: Many aftermarket cams shift the torque curve higher, but a well-matched cam can also increase area under the curve, making the engine feel stronger across a wider RPM range.

Keep in mind that a cam swap alone does not guarantee 50+ RWHP. You must pair the cam with a proper intake, exhaust, and a custom ECU tune to unlock the full potential.

Choosing the Right Camshaft for Your .4 HEMI

Selecting the correct camshaft is the most important decision you will make. The .4 HEMI family (starting with the 5.7L Eagle in 2009 and all 6.4L Apache engines) uses variable valve timing (VVT) and often multi-displacement system (MDS) lifters. Your cam choice must accommodate these systems unless you intend to delete them.

Camshaft Stages Explained

Cam manufacturers like Comp Cams and Texas Speed & Performance offer multiple stages:

  • Stage 1 (Mild): Duration around 210–220 degrees at .050″, lift .550–.590″. Retains VVT and MDS. Gains 30–40 RWHP, stock-like idle, good for daily drivers.
  • Stage 2 (Moderate): Duration 220–235 degrees at .050″, lift .600–.630″. Can retain VVT, but MDS is often deleted. Gains 50–70 RWHP, noticeable lope, needs a tune.
  • Stage 3 (Aggressive): Duration 235–255 degrees, lift .630–.670″. Typically requires VVT delete (lockout kit) and non-MDS lifters. Gains 70–90+ RWHP, rough idle, requires higher stall converter if automatic.

For most street cars wanting a reliable 50+ RWHP gain with a good idle, a Stage 2 cam retaining VVT is the sweet spot. Consider lobe separation angle (LSA) – tighter LSAs (110–112) increase power but hurt idle quality; wider LSAs (114–116) smooth out idle and improve vacuum.

VVT Phaser Considerations

The .4 HEMI uses a cam phaser that can adjust timing independently. If you choose a cam designed for VVT, you must reuse your factory phaser or buy a compatible aftermarket one. If you go with a solid cam and delete VVT, you will need a phaser lockout plate (e.g., from HP Tuners) and software to disable VVT. Many tuners recommend keeping VVT for street cars because it allows low-RPM torque and good fuel economy.

Tools and Materials Needed

Do not begin until you have all the correct tools and parts. Missing a specialized tool mid-project can stall you for days.

  • Tools:
    • Full metric and SAE socket set (3/8″ and 1/2″ drive)
    • Torque wrench (ft-lb and in-lb ranges)
    • Camshaft removal tool (HEMI-specific, available from specialty retailers)
    • HEMI VVT phaser holding tool (to prevent rotation during bolt removal)
    • Timing chain dampener tool or chain wedge
    • Pry bars and gasket scraper
    • Engine support bar or hoist (to lift engine slightly for cam removal)
    • Dial indicator and degree wheel (to verify cam timing if degreeing)
  • Materials:
    • New camshaft (recommended: stage 2 with VVT provision)
    • Camshaft timing chain set (Mopar OEM or high-performance chain like Cloyes – avoid cheap imports)
    • New head gaskets, timing cover gasket, intake manifold gaskets
    • Valve cover gaskets (rubber style preferred)
    • Assembly lube (white lithium or moly-based)
    • Engine oil (break-in oil like Brad Penn 10W-30, or conventional 5W-30 with high zinc)
    • Coolant (OEM Mopar or equivalent)
    • New spark plugs (if due, gap to spec)
    • Fuel injector O-rings (if removing intake manifold fuel rail)
    • Thread locker (blue Loctite)
    • Engine degreaser and shop towels

Preparation for the Cam Swap

Proper preparation saves hours and prevents mistakes. Work in a clean, well-lit area with plenty of room to lay out parts. Allow at least two full weekends for a first-time swap.

  1. Disconnect the Battery: Remove the negative terminal and isolate. Wait 10 minutes for the PCM capacitors to discharge.
  2. Drain Engine Oil and Coolant: Remove the drain plug on the oil pan (if accessible) and drain coolant from the radiator petcock and block drains. Dispose properly.
  3. Remove the Intake Manifold: Unbolt the intake using correct sequence. Label all vacuum lines and wiring connectors. Bag the bolts.
  4. Remove Valve Covers: Unbolt the coils and harnesses, then lift the valve covers. Note any broken gasket pieces that may fall inside.
  5. Set Engine to TDC: Rotate the crankshaft to top dead center on cylinder #1 (compression stroke). Remove the spark plug #1 and feel piston position using a long screwdriver or borescope.

Important Safety Note: The HEMI engine is heavy at the front. Support the engine with a hoist or jack under the oil pan (with a block of wood) before removing any engine mount bolts. When lifting, avoid putting pressure on the fuel lines or radiator.

Step-by-Step Cam Swap Process

This expanded section covers every detail for a 6.4L HEMI (similar for 5.7L with minor differences in phaser bolt size).

1. Remove the Timing Cover and Chain

  • Remove the crankshaft harmonic balancer using a puller. Secure the flywheel/flexplate to prevent rotation.
  • Unbolt the oil pan (you may lower it slightly without removing fully) to access the front cover bolts.
  • Remove all timing cover bolts – there are many, including two hidden behind the water pump. Use a schematic.
  • Gently pry the cover off. Clean off old sealer from the block and cover.

2. Remove the VVT Phaser and Cam Sprocket

  • Use the VVT holding tool to keep the phaser from rotating. Remove the center bolt (reverse thread? Check service manual – many HEMIs have standard thread but high torque).
  • Slide the phaser off the cam snout. Be careful with the phaser oil seals.
  • Remove the timing chain guide and tensioner. Keep the chain and guide orientation as they are.
  • Remove the cam sprocket from the back of the phaser (if separate).

3. Remove the Old Camshaft

  • The camshaft must slide out through the front of the block. On most .4 HEMIs, you must remove the front engine mount and possibly lift the engine slightly to clear the radiator support.
  • Rotate the cam while pulling gently to avoid hitting bearings. If resistance is felt, check for obstructions.
  • Inspect the bearings and journals. If bearings are scored, consider replacing them (requires specialized tools).

4. Install the New Camshaft

  • Liberally apply assembly lube to all cam lobes and bearing journals. Do not skimp.
  • Lubricate the cam snout and the phaser bore. Carefully slide the cam into the block while rotating to align lobes. Use a plastic mallet if needed, but never force it.
  • Reinstall the timing chain and sprocket, aligning the timing marks. On HEMI VVT engines, the phaser may have alignment marks relative to the camshaft dowel pin. Consult cam instructions – some aftermarket cams use multiple timing slots.
  • Torque the phaser bolt to specification (typically 85–95 ft-lb plus 90 degrees). Apply blue Loctite.
  • Install the timing chain tensioner and guide. Verify slack is within spec.
  • Rotate the engine two full turns by hand using a socket on the crank hub. Recheck timing marks. If all align, you are good. If not, you may need to degree the cam.

5. Reassembly

  • Clean the oil pan gasket surface and install a new gasket. Raise the pan back into place and torque bolts.
  • Apply a thin bead of RTV to the timing cover mating surface. Install the cover and torque in sequence.
  • Reinstall the harmonic balancer, using the correct installation tool (do not hammer). Torque the bolt to 148 ft-lb for 6.4L.
  • Install new valve cover gaskets, intake manifold gaskets, and spark plugs.
  • Reattach all sensors, vacuum lines, and fuel injectors. Replace O-rings as needed.
  • Fill with new engine oil (use a break-in oil with high zinc for the first 500 miles). Fill coolant.
  • Reconnect the battery but do not start yet.

Post-Swap Considerations

Your mechanical work is done, but the engine is far from ready to drive. Follow these steps in order.

  1. Prime the Oil System: Before cranking the engine, disable the ignition and fuel (pull fuel pump relay and disconnect coils). Crank the engine in 15-second bursts with 30-second cool-downs until you see oil pressure on the gauge. This prevents dry start-up damage.
  2. Initial Start: Re-connect fuel and ignition. Start the engine and let it idle at 1500–2000 RPM for the first 20 minutes to break in the camshaft lobes. Do not let it idle lower than 1200 RPM for the first 10 minutes. Monitor for oil pressure, coolant temperature, and leaks.
  3. Check for Leaks: After engine cools, inspect all gaskets and hose clamps. Pay special attention to the timing cover and front crank seal.
  4. Oil Change after First 20 Minutes: Some builders recommend draining the break-in oil after initial cam break-in and replacing with fresh conventional oil. This removes metal particles.
  5. ECU Tuning – Mandatory: A cam swap without a tune will cause a check engine light, poor idle, reduced power, and potential engine damage. You must have the ECU calibrated for the new cam timing, fuel trims, and idle settings. Use a reputable tuner like HP Tuners or a local shop. A canned tune from the cam manufacturer is a good starting point, but custom dyno tuning yields the best results and safety.
  6. Break-in Period: Drive gently for the first 500 miles. Avoid sustained high RPM or full throttle. Vary engine speed. After 500 miles, perform another oil change using synthetic 5W-30 or 0W-40 (check cam manufacturer recommendation).

Expected Results – What 50+ RWHP Looks Like

On a 6.4L HEMI with long-tube headers, cold air intake, and a Stage 2 cam (with VVT), dyno graphs typically show peak RWHP rising from 420–440 stock to 490–520. Torque may drop slightly at low RPM but gains above 3500 RPM can exceed 60 ft-lb. On a 5.7L, gains are proportionally similar, moving from 350–370 to 400–430 RWHP.

Real-world reports from forums like Charger Forum often confirm 50–70 RWHP gains with a proper setup. Your specific numbers depend on cam choice, tuning quality, and exhaust setup. Do not expect 50+ RWHP from a cam swap alone – headers and a tune are usually needed to unlock the full potential.

Common Mistakes to Avoid

  • Skipping the Cam Degreeing: Even pre-ground cams can be off a degree or two due to manufacturing tolerance. Degreeing the cam ensures optimal power.
  • Reusing Old Lifters with a New Cam: .4 HEMIs use roller lifters, but MDS lifters can fail with aggressive lobes. Replace lifters with non-MDS units if deleting MDS, or use high-quality OEM replacements.
  • Incorrect Phaser Wiring: If you delete VVT, you must remove the phaser electrical connection and correctly disable it in the tune. A mis-wired VVT system can cause limp mode.
  • Inadequate Oil Pump: High-lift cams can increase oil demand. Consider upgrading to a high-volume oil pump if using a very aggressive cam and high RPM operation.
  • Ignoring Cooling System: More power generates more heat. Ensure your radiator and fans are in good condition and consider a 180° thermostat.
  • Not Cleaning the Oil Pan: Metal shavings from cam bearing installation can collect in the pan. Remove the pan and clean it thoroughly before reassembly.

Conclusion

The .4 HEMI cam swap is a challenging but highly rewarding project. By carefully selecting the right cam for your goals, gathering the correct tools, and following each step with attention to detail, you can safely achieve 50+ rear-wheel horsepower gains. Do not rush the break-in or neglect the ECU tune – these are non-negotiable for longevity and performance. Whether you are building a weekend cruiser or a street-driven monster, a well-executed cam swap transforms the character of your HEMI. For further reading and community support, visit dedicated Mopar forums and reputable performance shops. Stay safe, take your time, and enjoy the power.