HEMI Lifter & MDS Delete Buyer's Guide: Prevention, Symptoms, Myths & Complete Parts Checklist

Understanding HEMI Lifters & The MDS System

Before we dive into failures and fixes, it's important to understand what we're dealing with. The Gen III HEMI uses hydraulic roller lifters—a proven design that's been around for decades. These lifters ride on the camshaft lobes and transfer that motion to the pushrods, which actuate the rocker arms and valves.

What Makes HEMI Lifters Different

Gen III HEMI lifters are grouped in sets of four within lifter yokes (also called lifter retainers or dog bones). These yokes keep the lifters aligned and prevent them from rotating—critical because roller lifters must stay oriented perpendicular to the camshaft. Each cylinder bank has four yokes holding 8 lifters (16 total per engine).

The lifters themselves are hydraulic, meaning they use engine oil pressure to maintain zero valve lash automatically. This eliminates the need for periodic valve adjustments and provides quiet operation—when everything is working correctly.

The MDS (Multi-Displacement System) Explained

Starting in 2005, Chrysler introduced the Multi-Displacement System (MDS) on 5.7L HEMI engines, later expanding it to the 6.4L. MDS is a cylinder deactivation system designed to improve fuel economy by shutting down four of the eight cylinders under light load conditions.

Here's how it works:

• Special MDS lifters on cylinders 1, 4, 6, and 7 contain an internal locking mechanism
• When the ECU commands deactivation, oil pressure unlocks these lifters
• The unlocked lifters collapse, preventing valve actuation on those cylinders
• Fuel and spark are cut to the deactivated cylinders
• The engine runs on 4 cylinders, reducing pumping losses and fuel consumption

On paper, it's clever engineering. In practice, it introduces additional complexity and potential failure points that many HEMI owners prefer to eliminate.

Why HEMI Lifters Fail: The Real Causes

HEMI lifter failures are real, but they're not random. Understanding the actual causes helps you prevent problems and avoid unnecessary repairs.

Oil Starvation & Contamination

The number one cause of lifter failure is inadequate lubrication. The roller bearing at the bottom of each lifter needs a constant supply of clean oil. When that oil supply is compromised, the bearing wears rapidly, leading to:

• Roller bearing surface degradation
• Increased friction and heat
• Needle bearing failure
• Roller seizure or disintegration

Common causes of oil starvation include:

• Extended oil change intervals – Dirty oil loses its protective properties
• Wrong oil viscosity – Too thick or too thin affects flow to critical areas
• Low oil level – Running even a quart low reduces oil pressure
• Clogged oil passages – Sludge buildup restricts flow to lifter galleries
• Failed oil pump – Rare but catastrophic when it happens

MDS Cycling Wear

MDS lifters have moving internal parts that engage and disengage thousands of times over the life of the engine. Each cycle creates wear on:

• The locking pin mechanism
• Internal oil sealing surfaces
• The lifter body bore

Over time, this wear can cause MDS lifters to stick in the collapsed (deactivated) position or fail to collapse when commanded. Both scenarios create valve timing issues and distinctive symptoms.

Manufacturing Defects

Early Gen III HEMI lifters (2003-2008) had documented quality issues. Chrysler issued TSBs (Technical Service Bulletins) addressing premature lifter wear. While manufacturing has improved significantly, some replacement lifters—particularly low-quality aftermarket options—still suffer from inadequate heat treatment or bearing quality.

Camshaft & Lifter Interface

The relationship between the camshaft lobe and the lifter roller is critical. Issues include:

• Aggressive cam profiles – Higher lift and faster ramp rates increase stress on the lifter roller
• Improper break-in – New lifters need proper seating with the camshaft
• Worn cam lobes – A damaged cam lobe can accelerate lifter wear

Symptoms vs Myths: What's Really a Lifter Problem?

The internet is full of misdiagnosis when it comes to HEMI engine noise. Here's how to separate genuine lifter issues from normal operation and other problems.

Real Lifter Failure Symptoms

The "HEMI Tick" Myth vs Reality

Let's address the elephant in the room: the infamous "HEMI tick."

The Myth: Any ticking noise from a HEMI means your lifters are failing and you need a complete valve train rebuild immediately.

The Reality: Gen III HEMIs are inherently noisy engines. Several normal sounds get misidentified as lifter problems:

• Exhaust manifold tick – The most common source. Broken exhaust manifold bolts or warped flanges create a tick that sounds exactly like a lifter. It's often louder when cold and may quiet down when warm.
• Injector noise – Direct-injection-style clicking from the high-pressure fuel system is normal.
• Rocker arm noise – Slight rocker arm clatter during cold starts is common and not harmful.
• MDS transition noise – A brief clatter when MDS activates or deactivates is normal operation.

Common Misdiagnoses

When It's Actually Time to Worry

Consider lifter inspection/replacement when you experience:

1. A tick that persists after the engine is fully warmed up and doesn't respond to oil changes
2. Misfire codes on MDS cylinders (1, 4, 6, 7) specifically
3. Visible metal contamination in your oil
4. A tick accompanied by reduced power or rough running
5. Codes related to camshaft/crankshaft position correlation

MDS Delete Explained: What It Is & Why People Do It

An MDS delete involves replacing the four special MDS (deactivating) lifters with standard non-MDS hydraulic roller lifters, then tuning the ECU to disable the MDS function. The result is an engine that runs on all eight cylinders, all the time.

Benefits of MDS Delete

• Eliminates MDS lifter failure risk – Non-MDS lifters have no internal locking mechanism to fail
• Smoother operation – No more transition between 4-cylinder and 8-cylinder modes
• Required for aftermarket camshafts – Performance cams aren't compatible with MDS operation
• Reduced complexity – Fewer moving parts means fewer potential failure points
• Consistent exhaust note – No more "burble" from uneven firing during MDS activation

Trade-offs to Consider

• Reduced fuel economy – Expect 1-3 MPG reduction in highway driving where MDS would normally activate
• Tuning required – The ECU must be reprogrammed to disable MDS; this is not optional
• Not a standalone fix – If you're doing an MDS delete, you might as well address all lifters for peace of mind

MDS Delete vs Full Lifter Replacement

Here's an important distinction:

• Partial MDS delete: Replace only the 4 MDS lifters with non-MDS units, keep the other 12 stock lifters
• Full lifter replacement: Replace all 16 lifters with upgraded non-MDS units

If you're going through the labor of removing the cylinder heads (required for lifter access on most HEMIs), replacing all 16 lifters makes sense. The incremental parts cost is minimal compared to the labor, and you'll have peace of mind knowing the entire valve train is fresh.

Prevention Strategies: Keeping Your Lifters Healthy

The good news? Most HEMI lifter failures are preventable. The factory MDS system can run reliably for 150,000+ miles when properly maintained. Here's how to keep your lifters healthy—whether you plan to delete MDS or not.

Oil Quality & Change Intervals

This is the single most important factor in lifter longevity. The MDS lifters rely on precise oil pressure and flow through tiny passages to activate and deactivate. Contaminated or degraded oil is the enemy.

• Use the correct viscosity: 5W-20 for most Gen III HEMIs (check your owner's manual). Don't "upgrade" to thicker oil thinking it protects better—it can actually starve the lifter mechanisms.
• Change intervals: 5,000 miles maximum for street-driven vehicles, regardless of what the oil life monitor says. If you do a lot of short trips or towing, drop that to 3,000-4,000 miles.
• Quality matters: Use name-brand synthetic oils that meet Chrysler MS-6395 specifications. Pennzoil Ultra Platinum and Mobil 1 are popular choices among HEMI owners.
• Don't forget the filter: Use a quality filter (Mopar, Wix, or equivalent) and change it with every oil change. A clogged filter restricts flow to the lifters.

Warm-Up & Driving Habits

How you drive—especially in the first few minutes—affects lifter health more than most owners realize.

• Let it warm up: Give the engine 30-60 seconds at idle before driving, and avoid heavy throttle until the engine reaches operating temperature. Cold oil doesn't flow as well through those tiny lifter passages.
• Avoid excessive idling: Extended idle time (especially with MDS cycling on and off) can cause uneven wear. If you're going to sit for more than a few minutes, shut it off.
• Drive it regularly: HEMIs that sit for weeks at a time are more prone to lifter issues. The oil drains from the lifters, and the first startup causes dry contact. If you're storing the vehicle, use a quality storage oil additive.

Address Warning Signs Early

A tick that starts intermittently and gets ignored becomes a catastrophic failure that takes out the camshaft, cylinder head, and sometimes the entire engine. If you hear something, investigate it.

• Cold start tick that goes away: Usually normal—this is often just oil draining from the lifters overnight. If it persists beyond 30-60 seconds, investigate further.
• Tick that appears at operating temperature: This is more concerning. It often indicates a lifter that's starting to fail or a collapsed lifter.
• Tick that changes with MDS activation: If the tick appears or disappears when MDS engages (usually around 1,200-1,500 RPM at light throttle), you likely have an MDS lifter issue specifically.

When Should You Delete MDS?

MDS delete isn't for everyone. Here's a straightforward breakdown of when it makes sense—and when you're better off leaving the system alone.

You Should Consider MDS Delete If:

• You're installing an aftermarket camshaft: This is non-negotiable. Aftermarket cams require non-MDS lifters, new valve springs, and supporting hardware. MDS delete is part of the package.
• You have a confirmed lifter failure: If you're already tearing the engine apart to replace failed lifters, it often makes sense to delete MDS entirely rather than risk another failure.
• You're building a performance engine: Stroker kits, forced induction builds, and serious NA power builds all benefit from eliminating the complexity of MDS.
• You tow heavy loads frequently: The constant MDS cycling under varying loads can accelerate wear. Tow vehicles often benefit from consistent 8-cylinder operation.
• You're experiencing persistent MDS-related issues: If you've had multiple solenoid failures, persistent DTCs, or other MDS-specific problems, deletion may be the permanent fix.

You Probably Don't Need MDS Delete If:

• Your engine runs fine with no symptoms: A properly maintained MDS system can last the life of the engine. "Preventive" deletion on a healthy engine is spending money to solve a problem you don't have.
• You're keeping the stock camshaft: If you're not doing a cam swap and have no lifter issues, there's little reason to delete MDS.
• Fuel economy matters to you: MDS provides a genuine 1-3 MPG improvement in highway cruising. Deleting it costs you at the pump.
• You want to maintain warranty coverage: MDS delete requires tuning changes that will void powertrain warranty coverage on newer vehicles.

Complete MDS Delete Parts Checklist

Whether you're doing a standalone MDS delete or combining it with a camshaft upgrade, here's everything you need. We've broken it down by scenario so you know exactly what applies to your build.

Standalone MDS Delete (Stock Cam)

This is the minimum required to delete MDS while keeping your factory camshaft:

MDS Delete with Camshaft Upgrade

This is the full list for a complete cam swap with MDS delete—the most common scenario:

Additional Recommended Items

These aren't strictly required, but experienced builders almost always replace them during the job:

• Timing chain and guides: If you're pulling the front cover anyway, fresh timing components are cheap insurance on high-mileage engines.
• Head gaskets: Only necessary if you're pulling heads, but worth noting.
• Rocker arms: Inspect for wear. Upgrading to 1.6:1 ratio rockers is a popular choice with cam upgrades.
• Oil pump: Consider a high-volume oil pump for performance builds, especially with aggressive cams.
• Valve cover gaskets: You'll have the covers off—replace the gaskets while you're there.

Installation Considerations

MDS delete and cam swaps are not beginner-level jobs. Here's what you need to know before deciding to DIY or hire a professional.

Skill Level Required

A standalone MDS delete (no cam change) is moderately difficult—it requires removing the cylinder heads to access the lifters. If you're comfortable with head gasket jobs, you can handle this.

A full cam swap adds complexity: timing the camshaft correctly, setting VVT phaser position, checking pushrod length, and verifying valve-to-piston clearance. Mistakes here can result in bent valves, damaged pistons, or worse.

Special Tools Required

• Valve spring compressor: Essential for removing and installing valve springs without removing heads (if doing in-car).
• Cam phaser timing tool: Required for VVT engines to lock the phaser in position during installation.
• Degree wheel and dial indicator: For properly degreeing the cam (highly recommended even if not strictly required).
• Torque wrench: Multiple sizes for various fasteners.
• Pushrod length checker: If using a different cam or machined heads, you need to verify pushrod length.

Time Estimate

For an experienced mechanic:

• Standalone MDS delete: 8-12 hours
• Cam swap with MDS delete: 12-16 hours

For a capable DIYer, double those estimates for your first time.

Tuning Requirements

Deleting MDS isn't just a hardware swap—it requires proper PCM calibration to prevent check engine lights, rough idle, and potential drivability issues. Without tuning, your engine computer will still attempt to activate MDS, sending oil pressure to lifters that can no longer respond. Here's what you need to know about getting your tune right.

What the Tune Must Address

A proper MDS delete tune needs to accomplish several things:

• Disable MDS activation commands – The PCM must stop sending signals to the MDS solenoids and stop attempting cylinder deactivation
• Adjust idle parameters – Without MDS, idle fuel trims and spark timing may need adjustment for smooth operation
• Clear MDS-related DTCs – Prevent check engine lights from codes related to the now-deleted system
• Recalibrate fuel tables – Your fuel economy will change slightly; the tune should optimize for all-8-cylinder operation

Tuning Options for MDS Delete

You have several paths to get your HEMI properly tuned after an MDS delete:

Handheld Tuners with MDS Delete Support

The easiest option for most enthusiasts is a handheld tuner with built-in MDS delete functionality. Devices like the DiabloSport inTune i3 can disable MDS through pre-loaded tunes, making this a plug-and-play solution for basic MDS deletes on otherwise stock engines.

Handheld tuners work well for:

• Stock or lightly modified engines (intake, exhaust, throttle body)
• Owners who want a simple, reversible solution
• Budget-conscious builds that don't require full custom tuning

Custom Remote Tuning

If you're combining MDS delete with other modifications—especially a camshaft upgrade—custom tuning is strongly recommended. Remote tuning works by:

1. You purchase a tuning device capable of reading and writing PCM files (like HP Tuners or DiabloSport's CMR system)
2. You send your stock PCM file to a professional tuner
3. The tuner creates a custom calibration for your specific combination
4. You flash the tune and datalog your results
5. The tuner refines based on your logs until the calibration is dialed in

Custom tuning is essential when your MDS delete is part of a larger build that includes camshaft, headers, ported heads, or forced induction.

Professional Dyno Tuning

For maximum performance and drivability, dyno tuning by an experienced HEMI tuner provides the best results. A skilled tuner can optimize every parameter in real-time while monitoring air/fuel ratios, knock, and power output. This is the gold standard for cammed engines and high-performance builds.

VVT Considerations in Your Tune

If your HEMI is equipped with Variable Valve Timing (2009+ 5.7L and all 6.4L 392 engines), your tune must also account for VVT behavior. Most MDS delete kits include a VVT phaser limiter or lockout, which restricts or eliminates camshaft phasing. Your tuner needs to know which component you've installed:

• VVT Limiter – Restricts phaser movement to a narrower range; tune should adjust VVT tables accordingly
• VVT Lockout – Completely locks the phaser at a fixed position; tune must disable VVT commands entirely

Running a VVT limiter or lockout without the corresponding tune adjustment will cause the PCM to constantly try to move the phaser, potentially triggering codes and creating idle quality issues.

Final Thoughts

HEMI lifter failure is a real concern, but it's not the epidemic some forums make it out to be. Understanding why lifters fail—oil quality, maintenance intervals, and the inherent weakness of the MDS collapse mechanism—empowers you to make informed decisions about prevention and repair.

For many owners, proactive MDS deletion provides peace of mind and eliminates a potential failure point before it becomes a problem. For others dealing with the dreaded "HEMI tick," a complete lifter replacement with quality non-MDS units is the path back to reliable operation.

Whatever your situation, remember these key takeaways:

• Don't just replace the camshaft – An MDS delete or cam swap requires lifters, springs, pushrods, VVT components, and proper tuning
• Quality components matter – Cheap lifters are a false economy when engine damage is the alternative
• Tuning is mandatory – Never run MDS delete hardware without the corresponding PCM calibration
• Consider doing it all at once – If you're pulling the valve covers anyway, a cam upgrade adds meaningful power for relatively little additional labor
• Maintenance is still king – Quality oil, proper intervals, and letting your engine warm up before aggressive driving extend the life of any valvetrain

The Gen III HEMI is a proven, capable platform that responds incredibly well to modifications. With the right parts, proper installation, and a quality tune, your HEMI will deliver reliable power for years to come. If you have questions about which components are right for your specific application, reach out to our team—we're here to help you build it right the first time.