Complete 5.7 Hemi MDS Delete Guide: Mechanical And Tuning Procedures

Successfully deleting the Multi-Displacement System (MDS) on a Chrysler 5.7L Hemi engine requires both a physical hardware replacement and an electronic computer calibration to prevent immediate engine damage and diagnostic trouble codes. Mechanically, you must install non-MDS lifters, a matching non-MDS camshaft, and physical block-off plugs in the lifter valley galleries. Electronically, the engine control module must be reflashed using a tuning interface to permanently disable the MDS solenoids and prevent cylinder-deactivation fault codes.

Pre-Operation Blueprint: Parts, Tools, and Budgeting for a 5.7 Hemi MDS Delete

Performing an MDS delete is an involved top-end and front-end engine overhaul. The Multi-Displacement System relies on oil pressure switched by solenoids to collapse special deactivating lifters on cylinders 1, 4, 6, and 7. Over time, these lifters are prone to roller bearing failure, causing the notorious Hemi tick and destroying the camshaft lobes.

To eliminate this vulnerability, you cannot simply unplug the solenoids or turn them off in the software. Leaving the spring-loaded MDS lifters in the engine while disabling their control will eventually lead to mechanical failure. You must perform a complete mechanical conversion.

Essential Equipment and Parts Checklist

• Mechanical Components:
  
  
  • Complete set of 16 non-MDS lifters (Mopar OEM or reputable aftermarket brands like Morel or Johnson).
  • Four non-MDS lifter guides/trays (MDS lifter trays have different indexing slots).
  • Non-MDS camshaft (factory non-MDS profile or an aftermarket performance camshaft).
  • Four MDS solenoid block-off plugs with fresh Viton O-rings.
  • New cylinder head gaskets and a complete set of torque-to-yield (TTY) cylinder head bolts.
  • Front timing cover gasket, water pump gasket, and crankshaft front seal.
  • New intake manifold gaskets and valve cover gaskets.
• Specialized Tools:
  
  
  • Calibrated click-type torque wrench (covering 10 in-lbs up to 150 ft-lbs).
  • Crankshaft damper puller (Hemi-specific three-jaw puller) and damper installation tool.
  • Torque angle gauge (for TTY head bolt installation).
  • Valve spring compressor tool (if swapping valve springs or seals).
  • Engine cleaning solvent, lint-free shop rags, and assembly lube.
• Electronic Calibration Tools:
  
  
  • Tuning device (such as HP Tuners MPVI3, DiabloSport Trinity, or a custom email tune loaded via a handheld programmer).
• Project Estimates:
  
  
  • Time Commitment: 12 to 18 hours of active garage time depending on experience, tool availability, and vehicle platform (Ram trucks generally offer more clearance than LX platform cars like the Charger or 300).
  • Financial Budget: $800 to $1,500 for DIY parts and tuning software; $2,500 to $4,500 if commissioned to a professional automotive performance shop.

Step-by-Step Mechanical and Electronic MDS Delete Execution

Step 1: Vehicle Prep and System Depressurization

Park the vehicle on a level surface, apply the parking brake, and disconnect the negative battery terminal. Drain the engine coolant completely by opening the radiator petcock or removing the lower radiator hose. Drain the engine oil to avoid contamination when pulling the cylinder heads. Remove the air intake assembly, throttle body, upper radiator shroud, and cooling fan module to maximize workspace at the front of the engine bay.

Step 2: Intake Manifold and Timing Cover Removal

Label and disconnect the fuel injector wiring harness, coil pack connectors, and vacuum lines. Relieve fuel system pressure via the Schrader valve on the fuel rail, then disconnect the fuel supply line. Remove the intake manifold mounting bolts in a crisscross pattern, lift the intake manifold assembly off the engine, and immediately cover the open cylinder head intake ports with clean painter's tape to prevent debris entry.

Remove the serpentine belt, alternator, power steering pump, and water pump. Use a Hemi-specific damper puller to remove the harmonic balancer. Unbolt and carefully pry off the front timing cover to expose the timing chain, tensioner, and camshaft sprocket.

Step 3: Cylinder Head Extraction

Remove the valve covers to expose the rocker arm assemblies. Loosen the rocker shaft bolts slowly and evenly, alternating one turn at a time to prevent bending the rocker shafts under valve spring pressure. Remove the pushrods, keeping them organized in a labeled cardboard box so they can be reinstalled in their exact original locations.

Loosen and discard the cylinder head bolts (these are torque-to-yield and cannot be reused). Carefully lift the cylinder heads off the engine block. Clean the block deck surfaces thoroughly using a brass gasket scraper or plastic disc. Do not use abrasive surface conditioning discs, as aluminum or steel grit can migrate into the oil passages and destroy the bearings.

Step 4: Solenoid Elimination and Block-Off Installation

With the cylinder heads removed, the lifter valley is fully accessible. Disconnect the electrical connectors from the four MDS solenoids located in the center of the lifter valley. Remove the retaining hold-down brackets and pull the solenoids straight up out of their bores.

[Note: Ensure the old rubber O-rings come out with the solenoids. If they remain stuck in the oil passages, retrieve them carefully with a brass pick.]

Lubricate the new MDS block-off plug O-rings with clean engine oil. Push the four block-off plugs firmly into the empty solenoid ports until they seat completely. Reinstall the solenoid hold-down plates and tighten the retaining bolts to 106 in-lbs (9 ft-lbs). These plugs seal off the high-pressure oil passages that formerly fed the deactivating lifter assemblies, maintaining consistent oil pressure to the main bearings.

Step 5: Camshaft and Lifter Upgrades

Pull the old lifter trays and lifters out of the block bores. If you are replacing the camshaft (which is mandatory because the lobe profiles on MDS cylinders are cut differently than non-MDS cylinders), align the timing marks on the crankshaft and camshaft gears to Top Dead Center (TDC).

Remove the timing chain, tensioner, and cam sprocket. Remove the camshaft thrust plate and carefully slide the old camshaft out of the block, taking care not to nick the inner camshaft bearings.

Generously coat the lobes and journals of the new non-MDS camshaft with high-quality assembly lube. Carefully slide the new camshaft into the engine block. Reinstall the thrust plate and torque the bolts to 132 in-lbs (11 ft-lbs).

Soak your new non-MDS lifters in clean engine oil for at least 30 minutes. Insert the new lifters into the new non-MDS lifter guides, ensuring the roller wheels align perfectly with the camshaft lobes. Slide the lifter guide assemblies down into the block bores and torque the lifter guide retaining bolts to 106 in-lbs (9 ft-lbs).

Warning: Never use standard MDS lifter guides with non-MDS lifters. The alignment flats on the lifter bodies are cut differently. Mixing them can cause a lifter to spin in its bore, leading to immediate engine failure and catastrophic camshaft wear.

Step 6: Engine Reassembly and Timing Alignment

Align the camshaft sprocket and crankshaft sprocket timing marks. Install the timing chain and tensioner, ensuring the alignment pins match up precisely. Install the front timing cover with a new gasket and front main seal. Torque the timing cover bolts to 250 in-lbs (21 ft-lbs).

Reinstall the harmonic balancer using a professional installation tool to draw it onto the snout of the crankshaft. Do not use the balancer bolt to draw it on, as this can strip the threads inside the crankshaft snout. Torque the balancer bolt to 130 ft-lbs.

Install the new cylinder head gaskets over the alignment dowels on the block deck. Set the cylinder heads in place. Install the new cylinder head bolts dry and hand-tighten them. Following the factory-specified torque sequence, torque the bolts in the multi-step sequence described in the technical specifications section below.

Reinstall the pushrods and rocker arm assemblies, torquing the rocker shaft bolts slowly and evenly to 16 ft-lbs (195 in-lbs). Reinstall the valve covers, intake manifold, fuel injectors, accessories, and cooling system components. Fill the engine with fresh 5W-30 engine oil (many builders prefer switching from the MDS-recommended 5W-20 to a slightly heavier 5W-30 or 5W-40 oil for superior wear protection once MDS is deleted) and premium coolant.

Step 7: Electronic Calibration via PCM Flashing

Do not attempt to start the engine without first flashing the Powertrain Control Module (PCM). The PCM will still expect to control the MDS solenoids and will look for feedback from the oil pressure sensor and solenoid circuits.

1. Connect your tuning interface (e.g., HP Tuners MPVI3) to the OBD-II port.
2. Turn the vehicle ignition to the "Run" position without starting the engine.
3. Open the tuning software on your laptop and read the stock calibration file from the PCM. Save a backup of this stock file.
4. Navigate to the "Engine" tab, then select the "Displacement On Demand" (DoD) or "MDS" parameters.
5. Change the master MDS enable switch from "Enabled" to "Disabled".
6. Navigate to the Diagnostic Trouble Codes (DTC) tab and set the error codes associated with the MDS solenoids (P1411, P1414, P1416, and P1417) to "No Error Reported" or "Disabled".
7. Save the modified calibration file under a new name.
8. Write/Flash the new calibration file back to the PCM.
9. Turn the ignition off, wait 30 seconds, then start the engine and check for oil leaks, mechanical noise, or check engine lights.

Pro-Tip: If you are running an aftermarket camshaft with increased lift or duration, you must also adjust the volumetric efficiency (VE) tables, idle airflow parameters, and spark advance curves within the software to ensure a stable idle and prevent lean operating conditions.

Hemi MDS vs. Non-MDS Technical Specifications and Torque Metrics

When converting a 5.7 Hemi engine, precision is the difference between a reliable engine and a bent valve. Refer to the table below for precise mechanical clearances, part cross-references, and torque limits.

Troubleshooting Common Post-Delete Complications

Scenario 1: Persistent Misfires on Cylinders 1, 4, 6, or 7 (Codes P0301, P0304, P0306, P0307)

• Root Cause: This is almost always caused by leaving the stock MDS camshaft in the engine while installing non-MDS lifters. Because the MDS camshaft lobe base circles are slightly different on the active cylinders, the valve lift and duration profiles will mismatch when using standard lifters. This causes improper valve seating, leading to compression loss and misfire codes.
• Actionable Fix: You must tear down the front of the engine and replace the MDS camshaft with a non-MDS camshaft (either a factory manual-transmission profile cam or an aftermarket performance profile).

Scenario 2: Low Oil Pressure Warning at Idle or Leaks in the Lifter Valley

• Root Cause: One or more of the MDS block-off plugs were installed without proper lubrication, causing the O-ring to pinch, tear, or roll out of its groove during insertion. This allows high-pressure oil to bleed off directly back into the oil pan, dropping the engine's main gallery oil pressure.
• Actionable Fix: Remove the intake manifold to access the lifter valley. Pull the block-off plugs, inspect the O-rings for cuts, replace damaged seals, lubricate with fresh engine oil, and reinstall them carefully.

Scenario 3: Engine Enters Limp Mode with Codes P1411, P1414, P1416, or P1417

• Root Cause: The mechanical delete was completed, but the electronic calibration was not correctly flashed, or the diagnostic trouble codes (DTCs) were not disabled inside the engine controller. The PCM is trying to ground the solenoid circuits to test them and is detecting an open circuit because the solenoids are physically missing.
• Actionable Fix: Reconnect your tuning software. Ensure the Master MDS flag is set to "Disabled" and that the specific diagnostic codes for all four solenoid circuits are set to "No Error Reported" or "Disabled" in the tune file, then write the program back to the PCM.

Frequently Asked Questions

Can I disable MDS with an electronic tuner without replacing any engine parts?

You can temporarily disable MDS electronically to prevent the engine from dropping into four-cylinder mode, but this does not prevent physical lifter failure. The spring-loaded locking pins within the MDS lifters can still wear out, stick, or fail structurally over time, even if they are never commanded to deactivate. A physical delete is the only true way to guarantee long-term engine reliability.

What happens if I don't change the camshaft during an MDS delete?

If you retain the MDS camshaft with non-MDS lifters, your engine will experience erratic valve timing, poor idle quality, and persistent cylinder misfire codes. The base circle on the MDS-deactivating lobes is engineered specifically to accommodate the unique travel distance of the collapsing lifters; using a standard solid lifter on these custom lobes prevents the valves from operating within factory lift tolerances.

Why do 5.7 Hemi MDS lifters fail so frequently?

MDS lifters fail primarily due to oil starvation at the roller bearings, combined with extended oil change intervals. The small, intricate oil passages feeding the lifter solenoids can easily become clogged with sludge. Additionally, idling for long periods reduces oil splash lubrication to the camshaft lobes, accelerating wear on the needle bearings inside the lifter rollers until they seize and scrape against the camshaft.

Will deleting the MDS system significantly decrease my fuel economy?

In real-world driving conditions, deleting the MDS system results in a negligible fuel economy penalty of approximately 1 to 2 miles per gallon, mostly noticeable during extended highway cruising. For most owners, the slight increase in fuel consumption is an easy trade-off for the massive increase in valvetrain reliability and the elimination of the engine-destroying "Hemi tick."

Technical Performance Upgrades and Sourcing

If you are ready to eliminate the weak links in your engine and restore its performance, invest in a premium, comprehensive conversion package. Browse our selection of custom non-MDS camshaft kits, high-performance lifters, and specialized tuning interfaces to build a durable, high-yield powerplant today.