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Manley Performance

Manley Chevrolet Big Block Exhaust Valve Kit - 1.850in Head Dia. 5.500in O/A Length, 0.3415in Stem

Manufacturer part number: 12339-8

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CODE: MAN12339-8
$401.42
$301.07 Backorder — not currently in stock Sold out
BACKORDER — not currently in stock

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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.

  • 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