By Admin 
Introduction
The 5.7 HEMI engine is one of Chrysler’s most iconic and widely used powerplants, known for its performance, durability, and distinctive hemispherical combustion chamber design. If you own a vehicle equipped with this engine—whether it’s a Dodge Charger, Challenger, Ram 1500, or Chrysler 300—you might be curious about its maintenance requirements, especially when it comes to spark plugs. One of the most frequently asked questions is: How many spark plugs in a 5.7 HEMI?
In this comprehensive guide, we’ll explore the answer to that question and provide detailed insights into why this engine uses more spark plugs than most, how often they should be changed, what types of plugs are recommended, and how to replace them yourself or with professional help.
How Many Spark Plugs Are in a 5.7 HEMI Engine?
The 5.7 HEMI engine uses 16 spark plugs—that’s two spark plugs per cylinder. This may come as a surprise to those accustomed to standard engines, which typically feature one spark plug per cylinder. Since the 5.7 HEMI is an eight-cylinder engine (V8), multiplying 8 cylinders by 2 spark plugs per cylinder gives you the total of 16 spark plugs.
Why Does the 5.7 HEMI Have 16 Spark Plugs?
There are a few engineering reasons behind this unique setup:
1. Better Combustion Efficiency
Each cylinder has two spark plugs to ensure more complete and even combustion. This design helps to ignite the air/fuel mixture more effectively, especially in the hemispherical combustion chambers that give the HEMI its name.
2. Improved Emissions
Dual spark plugs help reduce emissions by promoting cleaner and faster burning of fuel. This meets more stringent emission regulations while maintaining performance.
3. Increased Power and Fuel Economy
By optimizing ignition timing and combustion, the engine can deliver better fuel economy and horsepower without sacrificing drivability.
4. Redundancy and Reliability
Having two spark plugs per cylinder reduces the risk of misfires and can improve reliability, particularly under heavy load or towing conditions.
Vehicles Equipped with the 5.7 HEMI Engine
The 5.7-liter HEMI V8 is used in a variety of vehicles under the Chrysler, Dodge, Jeep, and Ram brands. Common applications include:
- Dodge Charger R/T
- Dodge Challenger R/T
- Chrysler 300C
- Ram 1500
- Jeep Grand Cherokee
- Dodge Durango
Each of these vehicles with the 5.7 HEMI engine will require 16 spark plugs during replacement.
When Should You Replace the Spark Plugs?
According to Chrysler’s official service schedule:
- Copper/Nickel Spark Plugs: Replace every 30,000–40,000 miles
- Iridium/Platinum Spark Plugs: Replace every 60,000–100,000 miles
It’s important to refer to your owner’s manual for the exact interval based on your spark plug type and driving conditions.
Signs Your Spark Plugs May Need Replacement:
- Engine misfires or rough idle
- Decreased fuel efficiency
- Difficulty starting the vehicle
- Engine knocking or pinging
- Illuminated check engine light
Recommended Spark Plugs for 5.7 HEMI
When replacing spark plugs, using the correct type is crucial for performance and longevity. The factory-recommended spark plug for the 5.7 HEMI is:
- OEM Part: Champion RE14MCC4 (Copper Core)
- Upgrades:
- NGK Iridium IX
- Denso Iridium TT
- Bosch Platinum or Double Iridium
Keep in mind that performance spark plugs often last longer but cost more.
Tools and Parts Needed for a Spark Plug Replacement
Tools:
- Ratchet and extension bars
- Torque wrench
- Spark plug socket (5/8-inch or 9/16-inch)
- Magnetic pickup tool (optional)
- Dielectric grease
- Compressed air (for cleaning around plug wells)
Parts:
- 16 spark plugs (matched to OEM specs)
- Anti-seize compound (optional, if recommended by the plug manufacturer)
Step-by-Step Guide to Replacing Spark Plugs in a 5.7 HEMI
Step 1: Prepare the Vehicle
- Park on a flat surface and let the engine cool completely.
- Disconnect the negative battery terminal for safety.
Step 2: Remove Engine Covers
- If your engine has plastic shrouds or covers, remove them to access the ignition coils and spark plug wells.
Step 3: Access Ignition Coils
- Each cylinder has two ignition coils (coil-on-plug design).
- Disconnect the electrical connectors and remove the mounting bolts.
Step 4: Remove Old Spark Plugs
- Use compressed air to clean around the plug wells.
- Carefully remove each spark plug using a socket and ratchet.
- Inspect plugs for signs of oil, carbon buildup, or damage.
Step 5: Install New Spark Plugs
- Apply dielectric grease to the ignition coil boots.
- Torque spark plugs to 13–15 lb-ft (check manufacturer specs).
- Reinstall coils and reconnect wiring harnesses.
Step 6: Reassemble and Test
- Reinstall engine covers and battery terminal.
- Start the engine to confirm smooth operation and no warning lights.
Cost of Replacing Spark Plugs in a 5.7 HEMI
DIY Cost:
- Spark plugs (copper): $2 – $5 each ($30 – $80 total)
- Spark plugs (iridium): $7 – $15 each ($120 – $240 total)
Professional Labor:
- 2–3 hours of labor at $75 – $150/hour = $150 – $450
Total Professional Cost: $200 – $700 depending on shop and plug type.
Tips and Best Practices
- Use a torque wrench to avoid overtightening.
- Label coils and wires if needed to avoid misplacement.
- Replace all 16 spark plugs at the same time for even performance.
- Check for engine updates or TSBs related to spark plug issues on your specific vehicle model.
Common Mistakes to Avoid
- Using the wrong spark plug type or heat range
- Not torquing plugs to proper specifications
- Reinstalling dirty or corroded ignition coils
- Neglecting to replace worn ignition coil boots
Conclusion
If you’ve ever wondered how many spark plugs in a 5.7 HEMI, the answer is 16—two per cylinder across its eight-cylinder layout. This unique setup is designed to improve combustion efficiency, reduce emissions, and maximize power. While replacing 16 spark plugs may sound like a lot, with the right tools and knowledge, it’s a manageable job for most DIY mechanics or a straightforward service for professional technicians.
Understanding your HEMI engine’s ignition system and maintaining it properly ensures long-lasting performance, reliability, and fuel efficiency. Whether you’re doing it yourself or visiting a repair shop, staying informed is the key to protecting your investment in one of the most powerful and respected V8 engines on the road today.