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This listing is for Manley 1.590" Diameter Pro Flo/Severe Duty Exhaust Valves Fits Chevy LT-1 6.2L

Part Number 12347-8

Manley performance products have been tearing up streets and tracks worldwide since 1966. Throughout the 1970s, legendary racers such as Don Garlits, Bill Jenkins, Joe Mondello, and “Jungle Jim” Liberman equipped their vehicles with Manley components. Today, Manley manufactures crankshafts, connecting rods, pistons, pushrods, rocker arms, valve springs, lash caps, guide-plates, and many high performance components. Unleash your street/strip machine’s true power potential with time-tested components from Manley.

Manley 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.

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