Challenger Spark Plug Change DIY: Step-by-Step for 5.7L and 6.4L

Tools Needed

• 5/8" spark plug socket (magnetic tip recommended)
• 3/8" drive ratchet and extensions (6" and 3" helpful)
• Torque wrench
• Dielectric grease
• Compressed air (optional but recommended)
• 16 spark plugs (the HEMI runs two per cylinder)

Parts to Buy

5.7L (pre-2009 single-plug): 8 plugs — NGK 6510 or Mopar SPZFR5C11

5.7L (2009+ dual-plug): 16 plugs — two types: NGK 6510 (conventional side) + NGK LZFR6AI (iridium hidden plugs)

6.4L: 16 plugs — NGK TR55 or equivalent

Check your specific year — early 5.7L used single-plug heads; later models switched to dual-plug for emissions.

Step-by-Step Procedure

Preparation

1. Let the engine cool completely — never work on hot plugs (risk of thread seizure)
2. Remove engine cover if present (usually 4 bolts)
3. Blow compressed air around each plug base to remove dirt before removing

Removal

1. Disconnect the coil-on-plug (COP) connector — press the tab and pull straight out
2. Remove the COP bolt (8mm)
3. Pull the COP straight up and out
4. Using the spark plug socket, loosen the plug counterclockwise
5. Remove plug, inspect the electrode (see note below)

Inspection

Look for:

• Gray/tan center electrode = normal combustion
• Black sooty = running rich
• White/chalky = running lean or overheating
• Oil fouling = rings or valve seals

Installation

1. Apply a small dab of dielectric grease to the inside of the plug boot
2. Thread the new plug in by hand — never cross-thread aluminum heads
3. Torque to 13 ft-lb (do not overtighten — strips aluminum threads)
4. Reinstall COP and bolt (8mm, snug)
5. Reconnect COP connector until it clicks

The Hidden Plugs on Dual-Plug HEMIs

The second set of plugs (Plug B) is located lower on the engine, accessible from below. You'll need:

• Car raised on jack stands
• Access from underneath the exhaust manifold area
• A different plug type (iridium, NGK LZFR6AI) specified for these positions

Many owners change only the accessible upper plugs and skip the lower ones — the lower plugs fire less frequently and last longer.