A healthy engine needs a healthy spark. If your 6.4 Hemi is starting to feel sluggish, misfire, or just isn’t running like it used to, your spark plugs might be the culprit. Swapping them out is a relatively simple job, and it can make a world of difference in performance and fuel economy. I’ve been wrenching on cars for years, and the 6.4 Hemi is a beast that deserves the right parts. Let’s take a look at some of the best spark plugs you can get for your engine to keep it purring like new.
Here’s a quick overview of my top picks:
- Best Overall: Champion Copper Plus 7989
- Best Performance: NGK 92184 Ruthenium HX
- Best Value: ACDelco 41-108 Iridium
- Best for Modified Engines: Brisk Racing Silver Spark Plug RR12S
- Best Budget Option: Autolite Copper Core 5224
Top 5 Best Spark Plugs for 6.4 Hemi Reviews
1. Champion Copper Plus 7989
The Champion Copper Plus 7989 is a solid, reliable spark plug that’s been around for ages. It’s a copper-core plug, which means it offers excellent conductivity and heat dissipation. This makes it a great all-around choice for the 6.4 Hemi, especially if you’re looking for a dependable plug at a reasonable price.
Pros:
- ✅ Excellent conductivity with copper core
- ✅ Affordable and readily available
- ✅ Good heat dissipation
Cons:
- ❌ Shorter lifespan compared to iridium or platinum plugs
- ❌ May require more frequent replacement
- ❌ Not ideal for heavily modified engines
Verdict: This is a great all-around plug for a stock or mildly modified 6.4 Hemi. If you want reliability and affordability, the Champion Copper Plus 7989 is a solid choice.
2. NGK 92184 Ruthenium HX
The NGK Ruthenium HX spark plugs are designed for maximum performance and longevity. Ruthenium is a precious metal that offers superior ignition and durability compared to traditional materials. If you’re looking to get the most out of your 6.4 Hemi, these plugs are worth considering.
Pros:
- ✅ Enhanced ignition performance
- ✅ Improved fuel efficiency
- ✅ Long lifespan due to Ruthenium construction
Cons:
- ❌ More expensive than copper or iridium plugs
- ❌ May not be necessary for stock engines
- ❌ Potential for diminishing returns if not properly gapped
Verdict: If you’re chasing every last bit of horsepower and want a long-lasting plug, the NGK Ruthenium HX is an excellent choice. These are great for tuned engines.
3. ACDelco 41-108 Iridium
The ACDelco 41-108 Iridium spark plugs offer a good balance of performance, durability, and price. Iridium is a very hard and durable metal, which allows for a thinner electrode design. This results in a more focused spark and improved ignition. Plus, they last a long time.
Pros:
- ✅ Long lifespan due to iridium construction
- ✅ Improved ignition performance
- ✅ Good fuel efficiency
Cons:
- ❌ More expensive than copper plugs
- ❌ May not offer the same level of performance as Ruthenium plugs
- ❌ Can be overkill for some engines
Verdict: The ACDelco 41-108 Iridium plugs are a great value for the money. They offer a good balance of performance, durability, and price, making them a solid choice for most 6.4 Hemi owners.
4. Brisk Racing Silver Spark Plug RR12S
The Brisk Racing Silver Spark Plug RR12S is designed for high-performance and racing applications. Silver is an even better conductor of electricity and heat than copper. This allows for a very strong and consistent spark, which is essential for highly modified engines. These are what you need if you have a supercharger or turbo.
Pros:
- ✅ Superior conductivity with silver electrode
- ✅ Excellent performance in high-performance engines
- ✅ Designed for racing applications
Cons:
- ❌ Very expensive
- ❌ Shorter lifespan compared to other materials
- ❌ May require frequent replacement
Verdict: If you have a heavily modified 6.4 Hemi and are looking for the ultimate spark plug, the Brisk Racing Silver Spark Plug RR12S is the way to go. Just be prepared to pay a premium and replace them more often.
5. Autolite Copper Core 5224
The Autolite Copper Core 5224 is a budget-friendly option that still offers decent performance. Like the Champion Copper Plus, it features a copper core for good conductivity. If you’re on a tight budget and just need a reliable replacement plug, the Autolite Copper Core 5224 is a good choice.
Pros:
- ✅ Very affordable
- ✅ Good conductivity with copper core
- ✅ Readily available
Cons:
- ❌ Shorter lifespan compared to iridium or platinum plugs
- ❌ May require more frequent replacement
- ❌ Not ideal for high-performance engines
Verdict: If you need a cheap and cheerful spark plug for your 6.4 Hemi, the Autolite Copper Core 5224 is a decent option. Just don’t expect the same level of performance or longevity as more expensive plugs.
Buying Guide
Choosing the right spark plugs for your 6.4 Hemi can seem daunting, but it doesn’t have to be. Here are a few key things to consider:
- Engine Condition: Is your engine stock, mildly modified, or heavily modified? Stock engines can usually get away with copper or iridium plugs, while heavily modified engines may require silver or Ruthenium plugs.
- Driving Style: Do you drive aggressively or conservatively? If you drive aggressively, you may want to consider a higher-performance plug.
- Budget: Spark plugs range in price from a few dollars to over twenty dollars each. Set a budget and stick to it.
- Lifespan: Copper plugs typically have a shorter lifespan than iridium or platinum plugs. Consider how often you’re willing to replace your spark plugs.
- Heat Range: The heat range of a spark plug refers to its ability to dissipate heat. Make sure you choose the correct heat range for your engine and driving conditions. A colder plug is better for performance applications.
- Gapping: Correctly gapping your spark plugs is crucial for optimal performance. Consult your vehicle’s owner’s manual or a trusted mechanic for the correct gap specification.
FAQs
Here are some frequently asked questions about spark plugs for the 6.4 Hemi:
Q: How often should I replace my spark plugs?
A: It depends on the type of spark plugs you have. Copper plugs typically need to be replaced every 30,000 miles, while iridium or platinum plugs can last up to 100,000 miles.
Q: What happens if I don’t replace my spark plugs?
A: Worn spark plugs can cause a variety of problems, including reduced fuel economy, misfires, and a loss of power.
Q: Can I install spark plugs myself?
A: Yes, replacing spark plugs is a relatively simple job that most DIY mechanics can handle. Just be sure to use the correct tools and follow the proper procedure.
Q: What is the correct spark plug gap for a 6.4 Hemi?
A: The correct spark plug gap for a 6.4 Hemi is typically around 0.043 inches. However, it’s always best to consult your vehicle’s owner’s manual or a trusted mechanic for the exact specification.
Q: Will better spark plugs increase horsepower?
A: While spark plugs themselves don’t directly add horsepower, using the right spark plugs for your engine and driving conditions can improve performance and fuel efficiency. In highly modified engines, high-performance spark plugs can help to maximize power output.
Conclusion
Choosing the right spark plugs for your 6.4 Hemi is essential for maintaining optimal performance and fuel economy. Whether you’re looking for a budget-friendly option or a high-performance plug for a modified engine, there’s a spark plug out there that’s perfect for your needs. Consider your engine condition, driving style, and budget to make the best choice for your vehicle. Happy wrenching!
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