Small Block Chevrolet Severe Duty Pro Flo Exhaust Valves - Set of 8 by Manley Performance
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°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.
In addition to the vastly superior strength and fatigue characteristics of Manley NK-844, our exclusive intake material exhibits an uncanny ability to resist chordal fractures. In an excellent sealing combustion chamber, the intake valve is actually deformed by the fuel explosion and pushed up into the port. The effect of this continuous deformation on competitors’ material eventually is a chordal fracture propagating from the circumference of the valve and quickly becoming a missing pie-shaped piece. Manley NK-844 is the absolute best choice of material to combat disastrous chordal fractures.
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 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.
Features
- Head Diameter: 1.600"
- Stem Diameter: .3415"
- Installed Height: Stock
- O/A Length: 4.936"
- Tip Length: .250"
- Underhead Angle/Radius: Pro Flo 12° x 3/8”
- Margin: .085"
- Seat Width: .080"
- Top of Head: 7° Dish
- XH-428 Stainless Material
- Chrome Stems and Hard Tips
- Swirl Polished and Fully Machined
Benefits
- Superior Stainless for High Temperature Gasoline Engines
- Exhaust Material XH-428 with Double the Ultimate Tensile Strength (at 1500°F) over the competition
- Up to 40% flow increase in small port OE style cylinder heads
- Proven performance improvement on the flow bench
Please Note: The image provided is generic and may not be an accurate representation of the product you will receive
