{"product_id":"manley-performance-12817-8","title":"Manley Performance Manley Chevrolet Big Block Exhaust Valve Kit - 1.900in Head Dia. 5.422in O\/A Length, 0.3110in Stem","description":"\u003cp\u003eManley Severe Duty® Valves deliver the ultimate in strength, reliability, and high-performance durability. Engineered for extreme gasoline engine temperatures, these valves are crafted from exclusive materials (XH-428 for exhaust and NK-844 for intake), offering unmatched tensile strength compared to competitive alloys. In fatigue testing at 40,000 psi and 1400°F, Manley exhaust valves endured 100 million cycles, while competitors failed after just 100,000, proving a 1,000× longer fatigue life. Each valve features chrome stems, hard tips, and swirl-polished underheads with fully machined combustion faces for superior airflow, efficiency, and wear resistance. Built for those who demand race-winning strength and precision, Manley Severe Duty® Valves set the industry standard for performance and endurance.\u003c\/p\u003e\u003cp\u003eGenuine Manley Performance. Part number 12817-8.\u003c\/p\u003e\u003cp\u003eImported to order from our US supply partner — allow 7-14 days delivery.\u003c\/p\u003e","brand":"Manley Performance","offers":[{"title":"Default Title","offer_id":62164925055363,"sku":"12817-8","price":311.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1018\/6506\/2787\/files\/639c017773af16048d25285e221903acL_e7463d1c-88f7-4d42-b898-0d4d541e5b9f.jpg?v=1785036768","url":"https:\/\/www.mlperformance.co.uk\/products\/manley-performance-12817-8","provider":"ML Performance","version":"1.0","type":"link"}