The Severe Duty series valves are signature pieces of Manley in the performance and racing industry.
Material XH-428 for exhaust valves and NK-844 for intake valves is offered by no competitor in the world.
No pair of materials shows such clear dominance over all others.
The ultimate tensile strength of XH-428 at 1500 DegreeF is nearly double that of the competitors' EV-8.
At 1000 DegreeF, 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 their comprehensive fatigue tests.
In normal operation where valve float is non-existent, a valve will experience 20,000 to 25,000 lbs.
of applied stress.
However, when valves bounce on the seat, the stress immediately soars to 40,000 to 60,000 lbs.
Manley exhaust valves (at 40,000 psi and 1400 DegreeF) ran to 100,000,000 (one hundred million) cycles while competitors' offerings failed at 100,000 cycles.
That's 1000 times better fatigue life.
