What Supporting Mods Does a HEMI Cam Swap Actually Require?

The Cam-Only Myth: Why It Doesn't Work That Way

If you've been researching HEMI camshaft upgrades, you've probably noticed that nobody sells "just a camshaft" for your 5.7L or 6.4L HEMI—and there's a good reason for that. Unlike some older pushrod engines where you could swap a cam and call it a day, the Gen III HEMI requires a specific set of supporting modifications to run an aftermarket camshaft safely and effectively.

This isn't marketing hype or upselling. It's engineering reality. The factory HEMI valvetrain was designed around the stock cam's lift, duration, and RPM range. Change the cam, and you're asking springs, lifters, and pushrods to do things they weren't built for. Skip the supporting mods, and you're looking at valve float, lifter failure, or worse—bent valves and a trashed engine.

The good news? Once you understand what's actually required versus what's optional, planning your cam swap becomes straightforward. Let's break down exactly what you need, what varies by application, and what's worth adding for the best results.

Mandatory Supporting Mods: The Non-Negotiables

Regardless of which stage camshaft you choose or what vehicle you're building, certain components are absolutely required for any HEMI cam swap. These aren't suggestions—they're the baseline for a safe, reliable installation.

High-Pressure Valve Springs and Retainers

Factory HEMI valve springs are designed for approximately .475" of lift. Aftermarket camshafts—even mild Stage 1 grinds—push lift into the .580"+ range. Without upgraded springs, you'll experience valve float at higher RPM, coil bind (where the spring compresses completely), and eventual valve-to-piston contact.

Performance valve spring kits are rated for .600"–.650" lift and provide the increased seat pressure and open pressure needed to control the valves through the cam's entire RPM range. Most camshaft kits include matched springs and titanium retainers specifically selected for the included cam profile.

Upgraded Pushrods

The increased lift and spring pressures of an aftermarket cam put significantly more stress on pushrods. Stock pushrods can flex under load, causing inconsistent valve timing and accelerated wear. Hardened chromoly pushrods—typically in both intake and exhaust lengths—are included in quality cam kits for this reason. For supercharged or nitrous applications, upgraded pushrods become even more critical.

VVT Phaser Limiter or Lockout

All 2009+ HEMI engines use Variable Valve Timing (VVT), which allows the factory ECU to advance or retard cam timing based on driving conditions. Aftermarket camshafts require either a phaser limiter (which restricts VVT movement to approximately 4 degrees) or a phaser lockout (which eliminates VVT function entirely).

• Stage 1–3 cams: Typically use a 4-degree phaser limiter
• Stage 4 cams: Require a complete phaser lockout due to aggressive timing events

Without the appropriate limiter or lockout, the phaser can move the cam into positions that cause piston-to-valve interference. Most cam kits include the correct phaser component for the included grind.

Phaser Installation Tool

Installing the phaser limiter or lockout requires a specialized tool to properly seat the component in the cam phaser. This is a one-time purchase that you'll need for the installation—don't overlook it when ordering your parts.

Conditional Requirements: What Varies by Application

Beyond the universal requirements, certain supporting mods depend on your specific engine, vehicle, and build goals. Understanding these conditional requirements helps you order exactly what you need—nothing more, nothing less.

MDS Delete Lifters (MDS-Equipped Vehicles Only)

If your HEMI has Multi-Displacement System (MDS)—the cylinder deactivation feature found on most 5.7L trucks and many 6.4L applications—you'll need to replace all 16 lifters with non-MDS performance lifters. The factory MDS lifters are designed to collapse on command, and they're not compatible with aftermarket cam profiles.

MDS delete lifters are solid, full-travel units that provide consistent valvetrain behavior across all operating conditions. This is also why cam swaps require a tune: the ECU must be recalibrated to stop sending MDS activation commands that would damage the new lifters.

Phaser Limiter vs. Lockout: Cam Stage Matters

As mentioned earlier, the choice between a phaser limiter and a complete phaser lockout depends on your camshaft's aggressiveness:

The phaser limiter preserves some of the factory VVT behavior (helping with low-RPM drivability and emissions), while the lockout fixes the cam timing at a set position. More aggressive cams need the lockout to prevent timing overlap that could cause valve-to-piston interference.

5.7L vs. 6.4L Considerations

While the overall supporting mod list is similar between engine families, pay close attention to component compatibility. Valve springs, pushrods, and lifters are often engine-specific, and cam kits are designed for either the 5.7L or 6.4L platform. The 6.4L's larger displacement and different head configuration mean you can't interchange these components between engines.

When ordering, always confirm your exact engine code (found on the emissions label or driver's door jamb) to ensure you receive the correct parts.

Optional but Recommended Upgrades

Once you've covered the mandatory supporting mods, there's a second tier of components that aren't strictly required but can significantly improve your results. These upgrades maximize the performance potential of your new cam while improving reliability and drivability.

Performance Torque Converter (Automatic Transmissions)

A camshaft changes where your engine makes power in the RPM range. Aftermarket cams—especially Stage 2 and above—shift the powerband higher, which means your stock torque converter may no longer be ideal. A performance torque converter with a higher stall speed allows the engine to launch at an RPM where the cam is actually making power.

For mild Stage 1 cams, the stock converter is usually acceptable. For Stage 2+ grinds, a converter with 2,800–3,500+ RPM stall (depending on cam aggressiveness) will dramatically improve acceleration and drivability. Without it, you may experience lazy launches and sluggish low-RPM response—the car will feel slower despite making more peak power.

Valve Seals

While you're replacing the valve springs, it makes sense to install fresh valve seals at the same time. The labor to access the valvetrain is the same, and new seals ensure proper oil control and prevent smoking issues down the road. Most quality spring kits include upgraded seals, but verify before ordering.

Timing Chain and Gasket Kits

Since a cam swap requires removing the front timing cover, many builders take the opportunity to replace the timing chain, tensioner, and guides—especially on higher-mileage engines. Fresh gaskets for the timing cover, valve covers, and oil pan are also worth including to prevent leaks after reassembly.

Intake and Throttle Body

An aftermarket camshaft improves airflow through the engine, but that airflow can be restricted by the factory intake manifold and throttle body. While not mandatory, pairing your cam with a performance intake manifold and larger throttle body allows the engine to fully realize its new breathing potential—especially in the upper RPM range where cammed engines thrive.

Long Tube Headers

Just as the intake side benefits from improved flow, the exhaust side can take advantage of the cam's improved scavenging characteristics. Long tube headers paired with an aftermarket cam create a synergy that unlocks significantly more power than either modification alone. This is especially true on NA builds where every bit of airflow counts.

Tuning: The Make-or-Break Factor

You can install the best camshaft on the market with every supporting mod done correctly, and your engine will still run poorly—or not at all—without proper tuning. This isn't an exaggeration. A cam swap absolutely, unequivocally requires a custom tune. No exceptions.

Why Tuning Is Non-Negotiable

An aftermarket camshaft fundamentally changes your engine's airflow characteristics, which affects fuel delivery, ignition timing, idle control, and emissions systems. The factory ECU calibration is built around the stock cam's behavior. Install a new cam without recalibrating, and you'll experience:

• Rough or unstable idle – The ECU doesn't know how to handle the different overlap and vacuum characteristics
• Check engine lights – Oxygen sensor readings won't match expected values
• Poor drivability – Hesitation, stumbling, and inconsistent throttle response
• MDS activation attempts – If not disabled, the ECU will try to collapse lifters that can no longer collapse, causing damage
• Potential engine damage – Incorrect fuel and timing can lead to detonation or lean conditions

Your Tuning Options

For HEMI cam swaps, you have two primary paths to proper calibration:

Handheld Tuners with Custom Tunes

Devices like the DiabloSport inTune 3 or Trinity 2 EX allow you to load custom calibrations created by professional tuners. Many cam kit manufacturers partner with experienced HEMI tuners to provide cam-specific tunes that work with the handheld device. This approach offers convenience and good results for most street applications.

The handheld also handles critical functions like disabling MDS, adjusting idle parameters, and recalibrating speedometer if you've changed tire sizes.

Professional Dyno Tuning

For maximum performance and precision, professional dyno tuning with HP Tuners or similar software allows a tuner to optimize every parameter for your specific combination. This is especially valuable for aggressive cams, boosted applications, or builds with multiple modifications. The tuner can watch real-time data and dial in air/fuel ratios, timing, and idle quality to perfection.

Build It Right the First Time

A HEMI cam swap is one of the most rewarding modifications you can do for your 5.7L or 6.4L—but only when it's done correctly. The aggressive lope at idle, the surge of mid-range torque, and the top-end pull that keeps going are all waiting for you. The key is understanding that a camshaft is a system upgrade, not a single bolt-on part.

Quick Reference: Supporting Mods Checklist

The Smart Approach: Complete Cam Kits

The easiest way to ensure you have everything you need is to purchase a complete camshaft kit that includes all mandatory supporting components—cam, springs, retainers, pushrods, lifters (if applicable), phaser limiter/lockout, and seals. These kits are engineered as a matched system, eliminating guesswork and compatibility concerns.

Trying to piece together individual components to save a few dollars often leads to mismatched parts, extra shipping costs, and installation delays when you realize something's missing. A quality cam kit gets you to the finish line faster and with fewer headaches.

Ready to give your HEMI the cam it deserves? Browse our complete camshaft packages to find the right kit for your build, or contact us if you need help selecting components. We're here to make sure your cam swap goes smoothly from start to finish.