NGK IX Iridium Spark Plug Box of 4 (TR55IX) - 7164

The NGK TR55IX Iridium IX Spark Plug (Part #7164) is an iridium-tipped performance spark plug engineered specifically for the performance enthusiast, and this listing includes a box of 4 plugs — enough for most four-cylinder applications or a partial set for larger engines. Designed to deliver a consistently stable spark in today's high-tech, high-performance engines, the TR55IX fits a wide range of domestic cars, trucks, and vans from manufacturers including Ford, Chevrolet, and GMC. If you're replacing worn plugs or upgrading from a standard copper or platinum plug, the NGK Iridium IX series is a well-regarded step up in ignition performance and longevity.

Key Features & Benefits

• Fine-wire iridium center electrode (0.6mm): The ultra-small diameter concentrates the spark for more reliable ignition, which translates to more consistent combustion and better throttle response — especially noticeable during cold starts and at idle.
• Extremely high melting point iridium alloy: Iridium's resilience to heat and wear means the electrode holds its shape longer than standard copper or platinum plugs, contributing to NGK's stated longevity rating of up to 50,000 miles.
• Projected fine-wire design: The projected tip positions the spark closer to the center of the combustion chamber, promoting more complete combustion and supporting fuel efficiency.
• Trivalent metal plating on the shell: Provides superior anti-corrosion and anti-seizing properties, making future removal easier — especially important in aluminum cylinder heads.
• Corrugated ribs on the insulator: Prevent flashover, reducing the risk of misfires caused by electrical leakage along the insulator surface.
• Pure alumina silicate ceramic insulator: Offers superior mechanical strength and better heat transfer compared to standard ceramic, helping the plug maintain its optimal heat range under varying load conditions.
• Copper core: Aids in heat removal from the firing tip, helping the plug self-clean and resist fouling.
• Triple seals: Prevent combustion gas leakage past the plug body, maintaining cylinder pressure integrity.
• Taper-cut nickel ground electrode: Works in conjunction with the fine-wire center electrode to reduce quenching and support a more complete spark event.
• Built-in 5k Ohm resistor: Suppresses electromagnetic interference (EMI) that can affect onboard electronics, sensors, and audio systems.

Specifications

• Part Number: TR55IX / NGK 7164
• Thread Diameter: 14mm
• Thread Pitch: 1.25mm
• Seat Type: Tapered (no gasket required)
• Reach: 18mm (0.709")
• Hex Size: 5/8" (16mm)
• Terminal Type: Solid
• Pre-set Gap: 0.059" (1.5mm)
• Center Electrode Material: Iridium, Fine Wire, 0.6mm diameter
• Electrode Projection: Projected
• Ground Electrode Material: Nickel, Standard, Taper Cut
• Resistor: Yes — 5k Ohm
• Heat Range: 5
• Torque Specs: Cast Iron head: 10.8–18 lb-ft | Aluminum head: 7.2–14.5 lb-ft
• Stated Longevity: Up to 50,000 miles
• Warranty: 60 days
• Quantity in this listing: Box of 4

Fitment

The NGK TR55IX (7164) fits a broad range of vehicles. The list below highlights confirmed applications from manufacturer fitment data — always use a year/make/model lookup to verify your specific engine before ordering:

• Ford E-150 — Base, XL, XLT (multiple model years)
• Ford E-250 — Base (multiple model years)
• Ford E-350 Super Duty — Base, XL, XLT (2015–2019 confirmed)
• Ford Transit Connect — XL, XLT, XLT Premium (2013 confirmed)
• Chevrolet Express 1500 — Base, LS, LT (2012–2014 confirmed)
• Chevrolet Silverado 1500 — Hybrid, LS, LT, LTZ, WT, XFE (2013 confirmed)
• GMC Savana 1500 — Base, LS, LT (2013–2014 confirmed)
• GMC Sierra 1500 — Denali, Hybrid, SL, SLE, SLT, WT, XFE (2013 confirmed)

This is not an exhaustive fitment list. The TR55IX applies across automotive, and potentially powersports, recreation, marine, and other applications. Use the fitment checker or contact our team to confirm compatibility with your specific year, make, model, and engine configuration before purchasing.

What's in the Box

• 4 × NGK TR55IX Iridium IX Spark Plugs (pre-gapped at 1.5mm / 0.059")

Why Buy from ThreePiece.us

At ThreePiece.us, we make it straightforward to get the right ignition parts without the hassle. Every order ships free — no minimum, no exceptions. Need to spread out the cost? We offer financing through Affirm, so you can check out now and pay over time. If you're unsure whether the NGK TR55IX is the right plug for your application, our team is here to help with fitment questions before you buy. We stock NGK plugs and carry them ready to ship, so you can get your tune-up completed on your schedule.

Frequently Asked Questions

Q: Does this listing include 4 spark plugs or just 1?
A: This listing is for a box of 4 NGK TR55IX plugs. If your vehicle requires more (for example, a V8 needs 8 plugs), simply adjust the quantity at checkout or contact us for bulk pricing guidance.

Q: Are the plugs pre-gapped, or do I need to gap them myself?
A: The TR55IX comes pre-set to a gap of 0.059" (1.5mm) from the factory. NGK generally advises against re-gapping fine-wire iridium plugs, as bending the delicate ground electrode can damage the iridium tip. Always verify your vehicle's specified gap against this pre-set gap before installation.

Q: What torque should I use when installing the TR55IX?
A: NGK specifies 10.8–18 lb-ft for cast iron heads and 7.2–14.5 lb-ft for aluminum heads. Because the TR55IX uses a tapered seat (no crush washer), it's especially important not to overtighten, as the tapered seat seals directly against the head. Always use a torque wrench.

Q: How long should NGK TR55IX iridium spark plugs last?
A: NGK rates the TR55IX for up to 50,000 miles of longevity. Actual service life can vary based on engine condition, fuel quality, and driving habits. Checking plugs at your manufacturer's recommended interval is always a good practice even with long-life iridium plugs.