Manley Chevy LS 3 L 99 (L 92 Head) 2.165in Head Diameter Pro Flo Intake Valves (Set of 8) Artofit. 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 1400F, 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. Swirl polishing and machined faces improved airflow optimized efficiency Exotic alloys for superior tensile strength, reliability, and longevity Proven fatigue strength for extreme performance Chrome stems and hard tips enhance durability