2019 Ram 3500 Spark Plug & Torque Specs

Quick Reference: 2019 Ram 3500 Spark Plug Specifications

Note: The 6.7L Cummins is a diesel engine and does not use spark plugs. It uses glow plugs for starting assistance in cold weather.

Why the Right Spark Plug Matters

Using the correct spark plug is critical for engine performance, fuel economy, and longevity. The engineers who designed your truck's ignition system selected a plug with a specific heat range, electrode material, and gap to ensure optimal combustion. Deviating from the factory recommendation can lead to misfires, poor mileage, and even engine damage.

• Heat Range: This refers to the plug's ability to dissipate heat. A "hotter" plug retains more heat, which can help burn off carbon deposits in a low-speed engine, while a "colder" plug dissipates heat more quickly to prevent pre-ignition (knock) in a high-performance engine. The 6.4L HEMI is a high-output engine that requires a specific, colder heat range to prevent detonation under load.

• Electrode Material: The OEM plugs for the 6.4L HEMI are long-life iridium-tipped plugs. While more expensive than platinum or traditional copper plugs, iridium offers superior durability and resistance to wear. This allows for the extended 100,000-mile service interval. Copper plugs provide excellent conductivity but wear out much faster, sometimes in as little as 30,000 miles. Using a copper plug in this engine would drastically shorten the service interval and may not provide the required spark intensity for complete combustion.

How to Gap a Spark Plug

Even when you buy pre-gapped plugs, it's crucial to verify the gap before installation. Plugs can be dropped during shipping, which can easily close the electrode gap.

1. Use the Right Tool: A ramp-style or feeler gauge is inaccurate for modern fine-wire plugs. Use a dedicated wire-loop or coin-style gapping tool.
2. Check the Gap: For the 2019 Ram 3500 with the 6.4L V8, the gap should be 0.043 inches (1.1 mm). Gently slide the tool between the center and ground electrodes. It should slide through with slight resistance. If it's too loose or too tight, it needs adjustment.
3. Adjust Carefully: To adjust, never pry against the fragile center electrode. Use the slot on your gapping tool to gently bend the ground electrode up or down. Make small adjustments and re-check the gap until it's perfect.

Replacement Procedure Tips for the 6.4L HEMI

The 6.4L HEMI uses a modern coil-on-plug ignition system, meaning each spark plug has its own ignition coil mounted directly on top of it. This provides a much stronger, more precise spark than an old-style distributor system.

• Coil Removal: After removing the engine cover, you'll see the eight ignition coils. Disconnect the electrical connector from the coil, then undo the small bolt holding the coil to the valve cover. The coil can now be gently twisted and pulled straight up to remove it from the spark plug.

• The Anti-Seize Debate: The OEM service information for many modern engines, including this one, advises against using anti-seize compound on the spark plug threads. The threads on the OEM plugs often have a special trivalent plating (usually black or gray) that prevents galling and corrosion. Applying anti-seize can act as a lubricant, leading you to inadvertently over-torque the plug, which can stretch the threads in the aluminum cylinder head. It can also interfere with the plug's electrical grounding. Our recommendation is to follow the manufacturer: install plugs clean and dry.

• Dielectric Grease: While you should skip anti-seize on the threads, applying a small amount of dielectric grease to the inside of the spark plug boot (the end of the ignition coil that connects to the plug) is highly recommended. This prevents the boot from sticking to the plug's ceramic insulator, makes future removal easier, and helps seal out moisture that could cause a misfire.

Known Issues

Fortunately, the 6.4L HEMI in the 2019 Ram does not suffer from major known issues related to spark plug replacement. Unlike the notorious Ford 3-valve Triton engines, where two-piece spark plugs frequently break off in the cylinder head, the HEMI uses a robust one-piece plug design that is far less prone to breakage.

By using the correct part and following proper procedures, a spark plug replacement on your Ram 3500 is a straightforward maintenance job.

Need plugs replaced? Find a shop on Repairius.