Challenger Spark Plug Change DIY: Step-by-Step for 5.7L and 6.4L
Changing spark plugs on the HEMI is straightforward but has a few gotchas. This guide covers both 5.7L and 6.4L procedures.
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
- Let the engine cool completely — never work on hot plugs (risk of thread seizure)
- Remove engine cover if present (usually 4 bolts)
- Blow compressed air around each plug base to remove dirt before removing
Removal
- Disconnect the coil-on-plug (COP) connector — press the tab and pull straight out
- Remove the COP bolt (8mm)
- Pull the COP straight up and out
- Using the spark plug socket, loosen the plug counterclockwise
- 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
- Apply a small dab of dielectric grease to the inside of the plug boot
- Thread the new plug in by hand — never cross-thread aluminum heads
- Torque to 13 ft-lb (do not overtighten — strips aluminum threads)
- Reinstall COP and bolt (8mm, snug)
- 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.
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