Manley Performance Big Block Severe Duty/Pro Flo 5.374in O/A Length Exhaust Valves - Set of 8 | Multiple Chevrolet Fitments (11831-8)

Big Block Chevrolet Severe Duty Stainless Steel 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 : 1.880
• Stem Diameter : .3715
• Installed Height : Stock
• O/A Length : 5.374
• Tip Length : .220
• Underhead Angle/Radius : Pro Flo: 10° x 3/8”
• Margin : .085
• Seat Width : .100
• Top of Head : 5° Dish
• Wgt/Grams : 132
• XH-428 Stainless Exhaust Material
• NK-844 Stainless Intake Material
• Chrome Stems and Hard Tips
• Swirl Polished and Fully Machined

Benefits

• Improved Flow with “Pro Flo” Underhead
• Best choice of material to combat disastrous chordal fractures
• 1000 times better fatigue life than competitors

Please Note: The image provided is generic and may not be an accurate representation of the product you will receive

Applications

• 1965, 1968–1974 Chevrolet Corvette
• 1965–1975 Chevrolet Chevelle
• 1967–1972 Chevrolet Camaro
• 1968–1970 Chevrolet Nova
• 1970–1975 Chevrolet Monte Carlo
• 1970–1975 Chevrolet El Camino
• 1965–1972 Chevrolet Biscayne, Chevrolet Bel Air, Chevrolet Impala, Chevrolet Impala SS
• 1965–1976 Chevrolet Caprice
• 1996–1999 Chevrolet Suburban 2500/GMC Suburban 2500

What's In The Box?

• 8 - Exhaust Valves

Warranty

• Manley products, due to their intended use, are sold without warranty.