Manley Performance is universally acknowledged as the leading manufacturer of performance and racing valves in the world.

The Severe Duty® series of valves is the Manley signature in the performance and racing industry. Exhaust material XH-428 and intake material NK-844 is offered by no competitor in the world. And no pair of materials show such clear dominance over all others. Ultimate tensile strength of XH-428 at 1500 Degree Fahrenheit is nearly double the competitors’ EV-8. At 1000 Degree Fahrenheit the Manley NK-844 displays more than four times the ultimate tensile of the competition’s best intake material. Further proof of the superiority of the Manley Severe Duty® valves is evident in our comprehensive fatigue tests. In normal operation where valve float is non-existent, a valve will experience 20,000 to 25,000 Pounds of applied stress. However, when valves bounce on the seat the stress immediately soars to 40,000 to 60,000 Pounds. Manley exhaust valves (at 40,000 PSI and 1400 Degree Fahrenheit) ran to 100,000,000 (One Hundred Million) cycles while competitors’ offerings failed at 100,000 cycles. That’s 1000 times better fatigue life.

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