Gen III Hemi MDS Delete Guide: How to Lock Out Multi-Displacement System for Long-Term Reliability

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Gen III Hemi MDS Delete Guide: How to Lock Out Multi-Displacement System for Long-Term Reliability

If you own a 5.7L or 6.4L Gen III Hemi, chances are you’ve either heard about the notorious "Hemi Tick" or experienced MDS-related valvetrain issues firsthand. Chrysler’s Multi-Displacement System (MDS) was engineered to improve fuel economy by shutting down four cylinders under light loads. However, the special collapsible hydraulic lifters used in MDS cylinders are a frequent point of failure in high-mileage engines—and they present a major obstacle when upgrading to a performance camshaft.

Whether you're repairing a collapsed lifter or installing an aftermarket cam, deleting the MDS system is one of the best moves you can make for the long-term reliability and performance of your engine.

Why Delete MDS?

  • Prevent Lifter Failure: Multi-Displacement System (MDS) lifters—common in engines like the Chrysler/Ram HEMI—fail primarily due to inadequate lubrication, long oil change intervals, and extended idling. While the MDS mechanism adds complex internal locking pins, the physical failure usually starts when tiny needle bearings in the lifter roller wheel seize or wear out, causing metal-on-metal grinding against the camshaft

  • Camshaft Options: Mopar has a few OEM camshaft options that will work will nonMDS lifters and require no special tuning other than disabling MDS.  Performance camshaft profiles require standard non-MDS lifters as well and will also require custom tuning. If you plan to upgrade your cam, an MDS delete is mandatory.

  • Consistent Engine Response: Deleting the system eliminates the lag and exhaust tone alteration when the engine transitions between 4-cylinder and 8-cylinder modes.

Required Parts & Hardware

Before teardown, make sure you have the following components on hand:

  • Non-MDS Lifters & Yokes: A full set of standard nonMDS roller lifters (such as Hellcat or 6.1L non-MDS style) and non-MDS lifter guides/trays.

  • MDS Solenoid Delete Plugs: 4 expansion plugs to replace the oil control solenoids located in the valley.

  • Head Gaskets & Head Bolts/Studs: Gen III Hemi head bolts are torque-to-yield (TTY) and must be replaced once removed.

  • Front Cover & Valve Cover Gaskets: Necessary for accessing the timing chain and camshaft.

  • PCM Tuning Solution: Diagnostic hardware/software or a custom tune to disable MDS in the ECU.

Step-by-Step Installation Overview

Note: Performing an MDS delete requires removing the cylinder heads and front timing cover. Ensure the engine bay is clean and the battery is disconnected before beginning.

Step 1: Top-End Disassembly

  1. Drain the engine coolant and oil.

  2. Remove the intake manifold, valve covers, coil packs, and pushrods. Organize pushrods by cylinder and valve position (intake and exhaust pushrods are different lengths on Gen III Hemi engines).

  3. Unbolt and remove the cylinder heads.

Step 2: Replace Lifters and Yokes

  1. Lift out the factory MDS lifters and plastic lifter guides.

  2. Inspect the camshaft lobes for wear or scoring. If a lifter failed, inspect the cam closely—a damaged lobe can also send metal through your oil.  This can damage your oil pump and bearings.  It is also a good idea to replace your oil pump with a HV style such as the Mopar OEM Hellcat or Melling 10452HV on 2009 and newer engines.  For earlier engines, use the Melling 10342HV.

  3. Dip your new non-MDS lifters in clean engine oil prior to installation.  

  4. Install the new lifters using the non-MDS lifter trays to ensure proper orientation.

Step 3: Install Valley Solenoid Delete Plugs

  1. Locate the 4 MDS solenoids in the engine valley (underneath the intake manifold).

  2. Unbolt and remove the factory solenoids.

  3. Clean the bores thoroughly and tap in the 4 MDS expansion delete plugs. These plugs block the oil passages previously used to feed the MDS lifters, maintaining stable oil pressure to the main oil gallery.

Step 4: Reassembly

  1. Clean the deck surfaces on the block and heads.

  2. Install new head gaskets and torque the new cylinder head bolts to factory specifications using the proper multi-stage torque angle sequence.

  3. Reinstall pushrods, rocker arms, front cover, intake manifold, and accessories. Refill all fluids.

Critical Step: ECU/PCM Programming

Mechanical deletion is only half the job. Once the engine is reassembled, you must disable the MDS function in the PCM via a tune or handheld tuner.  Keep in mind that 2015 and newer computer require unlocking prior to being able to reflash them.

If you start the engine without turning MDS off in the software, the PCM will still attempt to actuate the system under light throttle. Because the oil passages are plugged and non-MDS lifters are installed, the computer will detect a misfire or valvetrain malfunction and trigger a Check Engine Light (CEL).

Get the Right Parts for the Job

Doing an MDS delete properly requires matched, high-quality hardware. We stock complete MDS Delete Kits, hardened pushrods, head gasket sets, and performance camshaft packages for 5.7L, 6.1L, and 6.4L applications.

Browse Gen III Hemi Engine Parts & MDS Delete Kits at AMS Racing