{"product_id":"denso-iridium-long-life-spark-plugs-3421-8-pack-043-1-1mm-gap-iridium-core-for-reliable-ignition","title":"Denso Iridium Long-Life Spark Plugs 3421 — 8-Pack .043\" (1.1mm) Gap, Iridium Core for Reliable Ignition","description":"\u003cp\u003e\u003cstrong\u003eThese are genuine Denso Iridium long-life spark plugs (model 3421), sold as an 8-piece set with a .043\" (1.1 mm) electrode gap for direct replacement in compatible engines.\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIf you need reliable ignition components for a maintenance job or tune-up, this boxed set of eight Denso 3421 spark plugs provides factory-quality parts and original packaging. Denso is an established OEM supplier, and the iridium-tipped electrodes in this model are engineered to deliver consistent spark performance and extended service life compared with standard copper plugs. This product listing covers the authentic Denso parts, shipped as a complete eight-plug pack intended to replace worn or failing plugs in vehicles that call for this specific part number and gap size.\u003c\/p\u003e\n\n\u003ch3\u003eHow do these Denso iridium plugs improve ignition consistency?\u003c\/h3\u003e\n\u003cp\u003eThe iridium center electrode offers a finer tip and higher melting point than conventional materials, which helps maintain a focused, steady spark over long service intervals. That focused spark enhances combustion stability under varying driving conditions without changing engine systems.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eIridium core center electrode for reliable spark delivery\u003c\/li\u003e\n  \u003cli\u003eFine tip design promotes efficient combustion\u003c\/li\u003e\n  \u003cli\u003eDurable construction resists wear and maintains gap\u003c\/li\u003e\n  \u003cli\u003eSold as a matched set of eight for uniform replacement\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWill these plugs fit my vehicle and how do I confirm compatibility?\u003c\/h3\u003e\n\u003cp\u003eThese are Denso part number 3421 with a .043\" (1.1 mm) factory gap; compatibility depends on your engine’s specified plug type and heat range. Always verify fitment against your vehicle’s service manual or the retailer’s confirmed-fit tool before purchase to ensure correct thread size, reach, and heat rating.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003ePart: Denso 3421, gap set to .043\" (1.1 mm)\u003c\/li\u003e\n  \u003cli\u003eConfirm thread size and reach with vehicle specifications\u003c\/li\u003e\n  \u003cli\u003eUse seller\/retailer fitment tools or OEM cross-reference lists\u003c\/li\u003e\n  \u003cli\u003eReplacement requires same heat range and seat type as original\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow should I install and maintain these spark plugs for best results?\u003c\/h3\u003e\n\u003cp\u003eInstall by hand-first threading to avoid cross-threading, then torque to the manufacturer’s specification using a torque wrench or a calibrated socket. Check and re-torque if the engine head is aluminum and follow routine inspection intervals to maintain optimal gap and performance.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eHand-thread before final torque to prevent damage\u003c\/li\u003e\n  \u003cli\u003eApply recommended torque from vehicle manufacturer\u003c\/li\u003e\n  \u003cli\u003eInspect gap and electrode condition at service intervals\u003c\/li\u003e\n  \u003cli\u003eReplace in matched sets when multiple plugs are fouled or aged\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat’s included in the box and why buy the 8-pack?\u003c\/h3\u003e\n\u003cp\u003eThis listing includes eight genuine Denso 3421 spark plugs, original packaging, and any small hardware packaged by the manufacturer. Purchasing the full set ensures all cylinders receive identical, factory-matched plugs—important for balanced engine performance and smoother operation.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eEight genuine Denso 3421 spark plugs in original packaging\u003c\/li\u003e\n  \u003cli\u003eIncludes manufacturer hardware where applicable\u003c\/li\u003e\n  \u003cli\u003eSold as direct-replacement components—no modification needed\u003c\/li\u003e\n  \u003cli\u003eConvenient for multi-cylinder engines and full-tune-up jobs\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho is this for: Mechanics, DIY enthusiasts, and fleet owners looking for OEM-quality ignition components will find this set suitable when the vehicle manufacturer specifies Denso 3421 or an equivalent iridium plug with a .043\" (1.1 mm) gap. Choose this eight-pack when you need consistent, long-life spark plugs for a complete tune-up of multi-cylinder engines and want the reassurance of authentic Denso parts.\u003c\/p\u003e\n\u003csection class=\"product-faq-snippet\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: What is the electrode gap of these Denso spark plugs?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: .043\" (1.1 mm) gap pre-set for Denso 3421 spark plugs.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Are these genuine Denso parts sold as a full kit?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes — this listing includes eight genuine Denso 3421 spark plugs with original packaging and hardware.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"Denso","offers":[{"title":"Default Title","offer_id":48081424580766,"sku":"B0721V9JYZ","price":117.06,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0781\/2041\/9486\/files\/denso-3421-front-packaging.jpg?v=1785803714","url":"https:\/\/northtrailauto.ca\/products\/denso-iridium-long-life-spark-plugs-3421-8-pack-043-1-1mm-gap-iridium-core-for-reliable-ignition","provider":"North Trail Auto","version":"1.0","type":"link"}