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Best Spark Plugs for Harley Davidson Twin Cam: Full Guide

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Spark plugs are small but essential components of any gasoline-powered engine, serving as the catalyst for the combustion that powers your machine. They deliver the electrical spark that ignites the air-fuel mixture within the engine’s cylinders. As with any vehicle, the performance of a Harley Davidson Twin Cam engine can be substantially influenced by the quality and condition of its spark plugs. Choosing the best spark plugs is crucial for achieving optimal engine performance, reliability, and longevity.

Opting for the ideal spark plug for a Harley Davidson Twin Cam engine depends on various factors like heat range, electrode material, and compatibility with the bike’s specific model. Riders should look for spark plugs that can handle the engine’s high heat and stress without faltering, ensuring smooth running across a multitude of riding conditions. Heat range is particularly important because a spark plug with the appropriate heat range for your motorcycle will operate at an optimal temperature to avoid fouling or pre-ignition.

When selecting spark plugs, quality can’t be compromised. Materials like iridium and platinum are preferred for their durability and longevity compared to standard copper spark plugs. Although these premium materials come at a higher cost, the investment usually translates to better engine performance and longer service intervals, which can lead to cost savings in the long run.

As we evaluate the myriad options available on the market, a combination of our hands-on experience and comprehensive testing informs our recommendations for the best spark plugs for Harley Davidson Twin Cam engines. Our objective is to ensure that every rider can enjoy a reliable and powerful ride without concerns of spark plug failure or inefficiency.

Read next:
Finding The Best Spark Plug Wires for Harley Davidson Bikes
Finding Best Oil for Harley Davidson Twin Cam Engines (Guide)
Harley Spark Plug Gap Chart: A Guide for Experienced Riders

Top Spark Plugs for Harley Davidson Twin Cam

When it comes to maintaining the powerful performance of your Harley Davidson Twin Cam, choosing the right spark plugs is critical. Our selection prioritizes high-quality options designed to deliver optimum combustion and efficiency. With the right set, you can ensure your motorcycle runs smoothly, with a reliable start and better fuel economy. Here’s our roundup of the best spark plugs that will keep your ride at its peak.

NGK Iridium IX DCPR7EIX Spark Plugs for Harley Twin Cam engines between 1999 and 2016

NGK Iridium IX Plugs for Twin Cam

If you’re aiming to enhance your Harley’s ignition efficiency, we highly recommend these NGK Iridium IX spark plugs based on our experience.


  • improved horsepower
  • pre-gapped for convenience
  • corrosion-resistant plating


  • slightly higher cost
  • gapping may require fine-tuning in some cases

Firing up my Harley with a fresh set of NGK Iridium IX DCPR7EIX Spark Plugs has never failed to deliver that gratifying, smooth start. From what we’ve noticed, the bike runs impeccably without a hitch, exhibiting a noticeable improvement in the performance. The sense of a well-tuned engine is evident as soon as you hit the throttle.

The installation wins points on ease. These plugs come pre-gapped, streamlining what would otherwise be a meticulous process. Despite that, it pays to double-check the gap—a quick look before they went in ensured they were spot-on for my Twin Cam.

While the investment in these plugs might pinch the wallet slightly more than conventional ones, the returns on engine performance and longevity translate to money well-spent over the long rides. For us, the iridium technology in these spark plugs is not just a fancy term—it’s a clear step up ensuring our Harley runs optimally across countless miles.

CNPAPC Double Iridium Spark Plugs for Twin Cam engines

CNPAPC Double Iridium Spark Plugs

We recommend these spark plugs for noticeable improvements in ignition and overall performance in your Harley Davidson Twin Cam.


  • provides more efficient fuel consumption
  • noticeably stable spark leading to smoother acceleration
  • long lasting due to the high melting point of the double iridium


  • might require adjustment of the gap before installation

Swapping out spark plugs on our Twin Cam was a breeze, and the difference was palpable right after firing up the engine. The bike idled more smoothly, and the response to the throttle was crisper. The promise of double iridium technology seems to hold true, delivering a performance that any enthusiast would appreciate.

On a recent long haul, we did notice a subtle but welcome difference in fuel economy. It wasn’t revolutionary, but any savings are a win. Every time we rolled on the throttle, the power delivery was consistent, without any hiccups or misfires.

However, remember to check and adjust the gap if needed before popping these plugs into your engine. While the majority fit without issue, we’ve heard from a few riders who faced compatibility problems. It’s worth double-checking the specifications for your specific model. Despite some reports of competing brands offering better outcomes, we found these CNPAPC spark plugs to be a solid upgrade, especially when considering their balance of cost and performance.

NGK 6046 Iridium Spark Plugs for the Harley Davidson Twin Cam

NGK Iridium Spark Plugs for Harley

We believe these spark plugs are a top-notch upgrade for any Harley-Davidson Twin Cam engine, offering unparalleled reliability and performance.


  • Enhances the bike’s start-up and overall engine smoothness
  • Shows notable longevity, even after thousands of miles
  • Improves fuel efficiency compared to standard plugs


  • higher Cost upfront than some traditional plugs
  • requires careful handling during gapping to avoid damage
  • may be considered overkill for casual riders not seeking high performance

After recently installing these NGK iridium spark plugs on our Harley Twin Cam, the difference in start-ups and engine performance was night and day. The engine fired up swiftly and ran exceptionally smooth, a testament to the spark plug’s high quality.

Throughout our long rides, the NGK plugs proved their worth with consistent performance. Iridium, being a harder material than the commonly used platinum, means these plugs can take the heat and stress of the road without faltering. Thrilled with the mileage improvement, we were convinced that despite the initial investment, we made a savvy decision.

Even though the price is steeper, the advantages these plugs offered in the long term negated the pinch to our wallets. For riders looking to get the most out of their Harley, these spark plugs are quite frankly a game-changer.

Buying Guide

When we consider purchasing spark plugs for a Harley Davidson Twin Cam, we examine several critical factors to ensure we make a well-informed decision. Our focus is on quality and compatibility to achieve optimal engine performance.


We first verify the spark plug fits our specific Twin Cam model. Getting the right fit ensures proper combustion and engine functionality.

  • Thread Size: We match the thread size to our engine’s specifications.
  • Heat Range: We choose a spark plug with a suitable heat range for our riding conditions.


The material of the spark plugs contributes to their longevity and performance. We prefer materials that provide good conductivity and heat control.

  • Copper: Good for heat transfer, though not as durable as other materials.
  • Iridium and Platinum: Offer a balance between longevity and performance, usually our go-to options.


We pay attention to features that can enhance the spark plug’s performance and our ride quality.

  • Electrode Design: A fine-wire electrode can provide a stronger spark.
  • Ribs: High-quality insulator design prevents flashover.

Gap Specification

To ensure a precise spark, we check the manufacturer’s gap specifications for our engine. Incorrect gap settings can lead to misfires and poor performance.

Spark Plug Gap:

Riding StyleGap Specification
StandardCheck manual
PerformanceCheck manual

Installation and Maintenance

We consider the ease of installation and the recommended maintenance intervals. A plug that requires less frequent changes can offer us better value and less downtime.

In summary, by evaluating these critical aspects, we choose spark plugs that provide reliability, efficiency, and the confidence of a well-performing Harley Davidson Twin Cam engine.

In this section, we answer the most common queries riders have regarding the best spark plugs for Harley Davidson Twin Cam engines, their maintenance, and performance impacts.

What are the advantages of using iridium spark plugs in a Twin Cam engine?

Iridium spark plugs provide superior ignitability and service life for Twin Cam engines. These plugs resist electrode wear and fouling, allowing for more stable engine performance over time.

How does spark plug selection vary for different Twin Cam engine sizes, such as the 88, 96, and 103 models?

Choosing spark plugs for different engine sizes involves considering the engine’s compression ratio and performance demand. The 88 may require a different heat range compared to the 96 and 103 models, which typically benefit from plugs that can handle higher power outputs.

What is the recommended replacement interval for spark plugs in a Harley Davidson Twin Cam?

Our Twin Cam engines typically require new spark plugs every 15,000 to 20,000 miles. However, this can vary based on motorcycle usage and riding conditions.

Are there specific spark plug brands that are recommended for use in Harley Davidson motorcycles?

For Harley Davidson Twin Cam engines, popular choices include Harley OEM spark plugs, NGK, and Denso. These brands are known for their reliability and optimal compatibility with Harley engines.

Can the choice of spark plugs impact the performance of a Harley Davidson Twin Cam?

Yes, the right spark plugs can improve engine performance. A well-chosen spark plug ensures efficient combustion, potentially improving throttle response and fuel economy.

What should one consider when choosing spark plugs for high-performance applications on a Harley Davidson?

For high-performance Twin Cam engines, consider spark plugs with a higher heat rating to handle increased combustion temperatures and to avoid pre-ignition. It’s also essential to pair the spark plug with the engine’s performance modifications to maintain reliability.