{"product_id":"5-piece-idler-pulley-set-billet-upgrade-for-m278-v8-bi-turbo","title":"5-Piece Idler Pulley Set – Billet Upgrade for M278 V8 Bi-Turbo","description":"\u003cdiv style=\"font-family: Arial, sans-serif; max-width: 900px; margin: auto; line-height: 1.65; color: #222; font-size: 16px;\"\u003e\n\u003c!-- Lead --\u003e\n\u003cp\u003eRestore and upgrade the belt system on your \u003cstrong\u003eM278 4.7L BiTurbo V8\u003c\/strong\u003e with this complete \u003cstrong\u003e5-Piece Billet Aluminum Idler Pulley Set\u003c\/strong\u003e. The factory plastic and aging stamped-steel pulleys on the E 550, CLS 550, S 550, SL 550, and other M278-equipped models are prone to wear, noise, and failure—especially as mileage rises or when the engine is tuned. This kit replaces them with \u003cstrong\u003eCNC-machined billet pulleys\u003c\/strong\u003e engineered for reliability, smooth operation, and long-term durability.\u003c\/p\u003e\n\u003c!-- Why It Matters --\u003e\n\u003cp style=\"margin-top: 10px;\"\u003eThe OEM idler pulleys on the \u003cstrong\u003eM278 4.7L V8 BiTurbo\u003c\/strong\u003e develop play, bearing noise, belt slip, and wobble over time. On a twin-turbo V8, even minor belt irregularities can cause \u003cstrong\u003eboost inconsistencies, charging issues, accessory failures, or catastrophic belt breakage\u003c\/strong\u003e. Upgrading to billet aluminum eliminates these weak points and stabilizes the engine’s entire accessory drive system.\u003c\/p\u003e\n\u003c!-- Key Features --\u003e\n\u003ch3 style=\"margin-top: 20px;\"\u003e🔧 Key Features – Billet Idler Pulley Set for M278\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCNC-machined 6061-T6 billet aluminum:\u003c\/strong\u003e Significantly stronger than OEM plastic or steel pulleys.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHard-anodized surface:\u003c\/strong\u003e Provides corrosion resistance and long-term bearing stability.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePremium high-speed bearings:\u003c\/strong\u003e Quiet, smooth rotation with improved temperature tolerance.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull 5-piece belt path refresh:\u003c\/strong\u003e Replaces all major M278 idlers for a complete system overhaul.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDirect bolt-on installation:\u003c\/strong\u003e Fits in place of factory pulleys with no modifications required.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImproves belt tracking:\u003c\/strong\u003e Reduces slip at higher loads and improves boost consistency.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMade in the USA:\u003c\/strong\u003e Precision-manufactured to motorsport-grade tolerances.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- Performance \u0026 Reliability Benefits --\u003e\n\u003ch3 style=\"margin-top: 20px;\"\u003e📈 Performance \u0026amp; Reliability Benefits\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eEliminates OEM pulley failure points\u003c\/strong\u003e that become common past 60k–100k miles.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReduces belt noise, squeal, and vibration\u003c\/strong\u003e for smoother accessory operation.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSupports tuned M278 engines\u003c\/strong\u003e running increased boost or upgraded coolers.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStabilizes boost control\u003c\/strong\u003e by preventing belt slip under acceleration.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExtends belt life\u003c\/strong\u003e by using precise billet alignment and higher-quality bearings.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- What's Included --\u003e\n\u003ch3 style=\"margin-top: 20px;\"\u003e📦 What’s Included\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e(5) CNC-machined billet aluminum idler pulleys (complete M278 set)\u003c\/li\u003e\n\u003cli\u003ePre-installed high-speed performance bearings\u003c\/li\u003e\n\u003cli\u003eOEM-spec mounting hardware (as required)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- Compatibility Table --\u003e\n\u003ch3 style=\"margin-top: 22px;\"\u003e✔️ Compatibility – M278 4.7L V8 BiTurbo\u003c\/h3\u003e\n\u003cp\u003eFits the following Mercedes-Benz models equipped with the \u003cstrong\u003eM278 4.7L BiTurbo V8\u003c\/strong\u003e:\u003c\/p\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse; margin: 10px 0 14px; font-size: 15px;\"\u003e\n\u003cthead\u003e\n\u003ctr style=\"background-color: #f2f2f2;\"\u003e\n\u003cth style=\"border: 1px solid #ddd; padding: 8px; text-align: left;\"\u003eChassis\u003c\/th\u003e\n\u003cth style=\"border: 1px solid #ddd; padding: 8px; text-align: left;\"\u003eModel\u003c\/th\u003e\n\u003cth style=\"border: 1px solid #ddd; padding: 8px; text-align: left;\"\u003eYears (Approx.)\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eW212\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eE 550\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e2012–2016\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eW218\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eCLS 550\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e2012–2018\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eW221 \/ W222\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eS 550\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e2011–2017\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eR231\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eSL 550\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e2013–2020\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eX166\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eGL 550 \/ GLS 550\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e2013–2019\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eW166\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eML 550 \/ GLE 550\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e2012–2019\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp style=\"font-size: 13px; color: #555; margin: 0 0 12px;\"\u003e*Some markets vary. If you’re unsure whether your Mercedes uses the M278 engine, send us your \u003cstrong\u003eVIN\u003c\/strong\u003e and we’ll confirm fitment before shipping.\u003c\/p\u003e\n\u003c!-- Recommended Mods --\u003e\n\u003cdiv style=\"margin-top: 20px; padding: 14px 16px; border-radius: 8px; border: 1px solid #eee; background: #f7f7f7;\"\u003e\n\u003cp style=\"margin: 0 0 8px;\"\u003e\u003cstrong\u003eRecommended supporting upgrades for the M278 4.7L BiTurbo:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul style=\"margin: 0 0 4px 18px;\"\u003e\n\u003cli\u003e\u003ca href=\"\/products\/m278-aluminum-intake-tubes\" style=\"color: #000; font-weight: bold; text-decoration: none;\"\u003e M278 Aluminum Intake Tubes \u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/m278-intake-filter-spacer-kit\" style=\"color: #000; font-weight: bold; text-decoration: none;\"\u003e M278 Intake Filter Spacer Kit \u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/custom-ecu-tuning-m278-4-7-biturbo\" style=\"color: #000; font-weight: bold; text-decoration: none;\"\u003e Custom ECU Tuning for M278 4.7L BiTurbo \u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/m278-turbo-blankets\" style=\"color: #000; font-weight: bold; text-decoration: none;\"\u003e M278 Turbo Blankets \u0026amp; Heat Management \u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c!-- Installation --\u003e\n\u003ch3 style=\"margin-top: 20px;\"\u003e🧰 Installation\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eDirect bolt-on replacement for all M278 idler pulley locations.\u003c\/li\u003e\n\u003cli\u003eTypical install time: 1–2 hours.\u003c\/li\u003e\n\u003cli\u003eNo tuning or reprogramming required.\u003c\/li\u003e\n\u003cli\u003eWorks with OEM and upgraded belt configurations.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- Trust Section --\u003e\n\u003ch3 style=\"margin-top: 26px;\"\u003e🏁 Designed, Tested \u0026amp; Proven on M278 Platforms\u003c\/h3\u003e\n\u003cp style=\"margin-top: 0;\"\u003eWith over \u003cstrong\u003e12 years\u003c\/strong\u003e of hands-on experience tuning and daily-driving Mercedes-Benz V8 BiTurbo engines, we know exactly where the M278 benefits from stronger hardware. This pulley set is built to meet the demands of real-world heat, boost, and mileage—offering a durable solution that improves reliability and performance across all 4.7L BiTurbo platforms.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BenzUnited Parts","offers":[{"title":"Default Title","offer_id":46285619953839,"sku":null,"price":540.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0631\/8718\/9935\/files\/5-piece-idler-pulley-set-m278-billet-upgrade.jpg?v=1763435434","url":"https:\/\/benzunitedparts.com\/products\/5-piece-idler-pulley-set-billet-upgrade-for-m278-v8-bi-turbo","provider":"BenzUnited Parts","version":"1.0","type":"link"}