Manley 11747-8 Severe Duty Exhaust Valve Small Block Chevy Stainless Steel

Designed for high-performance and racing use, these valves are manufactured from Manley's proprietary XH-428 exhaust valve material — a high-temperature alloy with nearly double the ultimate tensile strength at 1,500°F compared to commonly used EV-8 competitor materials.

Manley's Severe Duty® valves have been subjected to rigorous fatigue testing. Under normal operating conditions, valves experience 20,000–25,000 lbs. of applied stress. During valve float or seat bounce, that load surges to 40,000–60,000 lbs. Manley exhaust valves, tested at 40,000 psi and 1,400°F, endured 100,000,000 cycles — compared to just 100,000 cycles for competing valves, demonstrating 1,000 times greater fatigue life.

Key Features:

• Material: XH-428 proprietary stainless steel — exclusive to Manley
• Head Diameter: 1.500 in.
• Stem Diameter: 0.3415 in.
• Overall Length: 4.911 in. (Stock Height)
• Valve Type: Exhaust
• Engineered for high-temperature gasoline engines in performance and racing applications
• Superior fatigue life — 1,000x better endurance vs. leading competitor exhaust valves
• Made in the USA by Manley Performance Products

The Manley Severe Duty® Series represents the gold standard in performance valvetrain components, trusted by professional engine builders and racers worldwide. The 11747-8 is a direct replacement or performance upgrade for Chevrolet Small Block V8 cylinder heads requiring a 1.500" exhaust valve.