{"product_id":"chenacc-ls-harmonic-balancer-bolt-12557840-for-gen-3-4-ls-engines","title":"CHENACC LS Harmonic Balancer Bolt 12557840 for Gen 3\/4 LS Engines","description":"\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eMeet the CHENACC LS Harmonic Balancer Bolt, a robust OEM-grade fastener designed to secure the harmonic balancer on Gen 3 and Gen 4 LS engines. With part references 12557840 and 917-139, this bolt is built to match the original hardware, delivering dependable fitment without guesswork. It combines precise threading and a durable build to support steady accessory alignment under typical driving conditions.\u003c\/p\u003e\n\u003cp\u003eDesigned to fit a wide range of LS models (LS1, LS2, LS3, LS6, L59, L92, L96, L99, LC9, LH8, LMF, LMG, LY5, LM7, LR4, LQ4, LQ9) and family brackets, this bolt helps you maintain a balanced engine bay when replacing worn or corroded fasteners. While LS7 and LS9 are not included in this lineup, the rest of Gen 3 and Gen 4 engines can benefit from a replacement that mirrors the original fastener's dimensions and threading, supporting reliable operation without overengineering.\u003c\/p\u003e\n\u003ch3\u003eKey features\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eOEM part numbers:\u003c\/strong\u003e 12557840, 917-139 align with the original hardware\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFitment:\u003c\/strong\u003e Gen 3 and Gen 4 LS engines including LS1, LS2, LS3, LS6, L59, L92, L96, L99, LC9, LH8, LMF, LMG, LY5, LM7, LR4, LQ4, LQ9\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial \u0026amp; coating:\u003c\/strong\u003e Grade 10.9 alloy steel with a protective Dacromet finish for rust and corrosion resistance\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSize \u0026amp; thread:\u003c\/strong\u003e M16 x 2 thread, 4.05 inch underhead for secure seating\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEase of use:\u003c\/strong\u003e Engineered for straightforward installation to replace an aging mounting bolt quickly\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eMaterials, coating, and durability\u003c\/h3\u003e\n\u003cp\u003eThe bolt uses premium Grade 10.9 steel, chosen for strength under load. The Dacromet coating adds rust resistance, making it well suited to engine bays where heat and humidity rise during daily driving or occasional track days. The combination aims to offer long-term reliability without compromising serviceability.\u003c\/p\u003e\n\u003ch3\u003eInstallation and guidance\u003c\/h3\u003e\n\u003cp\u003eDesigned with user-friendly installation in mind, this fastener is compatible with standard LS-bolt installations. Align the bolt with the harmonic balancer and torque to the manufacturer’s specification. This approach can help minimize install time and avoid cross-threading during replacement.\u003c\/p\u003e\n\u003ch3\u003eWhy CHENACC\u003c\/h3\u003e\n\u003cp\u003eCHENACC provides a match for OEM specifications and a clean engine bay appearance. The part numbers 12557840 and 917-139 are included to help you verify correct fitment. Consider this bolt if you’re refreshing components as part of an engine maintenance routine or rebuild planning.\u003c\/p\u003e\n\u003ch3\u003eNotes\u003c\/h3\u003e\n\u003cp\u003eReview your engine family and the assembly you’re working on to confirm fitment. This bolt is not intended for LS7 or LS9 configurations.\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 engines is the CHENACC LS Harmonic Balancer Bolt compatible with?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Designed for Gen 3 and Gen 4 LS engines; not for LS7 or LS9. Verify with OEM numbers 12557840 or 917-139.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: What makes this bolt durable and easy to install?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Grade 10.9 steel with a Dacromet coating provides corrosion resistance; installation is straightforward with standard tools.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"CHENACC","offers":[{"title":"Default Title","offer_id":42465436631125,"sku":"B0DBH7738C","price":27.88,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0632\/3270\/4597\/files\/chenacc-ls-harmonic-balancer-bolt-12557840-closeup.jpg?v=1778007864","url":"https:\/\/plentytorque.co.uk\/products\/chenacc-ls-harmonic-balancer-bolt-12557840-for-gen-3-4-ls-engines","provider":"PlentyTorque","version":"1.0","type":"link"}