Pro Flo Undercut Valve Stem Design
Manley Performance is indisputably a leading manufacturer of performance and racing components in the world. The reason for Manley's overwhelming success is simple: Quality. Manley offers the best materials in the industry - exclusive materials that other manufacturers do not possess. Manley's valve stems are hard coated with .0002'' thick chrome rather than a few millionths of flash. Manley's hard valve tips are superior to competitors' puddled ''stellite'' which can crack and erode off the stem. Manley's valve head and under head shapes have been in the forefront of the quest for improved flow since the late 1960's.
The Severe Duty series valves are Manley's signature pieces in the performance and racing industry. Exhaust valve material XH-428 and intake valve 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°F is nearly double the competitors' EV-8. At 1000°F 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°F) ran to 100,000,000 (one hundred million) cycles while competitors' offerings failed at 100,000 cycles. That's 1000 times better fatigue life.
- Superior Stainless for High Temperature Gasoline Engines
- Intake Material NK-844 with 1000 Times Better Fatigue Strength than competitors' offerings
- Exhaust Material XH-428 with Double the Ultimate Tensile Strength (at 1500°F) over the competition
- Chrome Stems and Hard Tips
- Swirl Polished and Fully Machined
- Severe Duty (Straight Stem) and Severe Duty Pro Flo (Undercut Stem) Shapes Available
- Improved Flow with ''Pro Flo'' Underhead Design and Lighter Weight