Manley Performance Dart Big Block Pro 1 Stock Length 11/32in Stem Diameter Severe Duty Exhaust Valves – Set of 8 | Multiple Fitments (11817-8) Manley Performance

Big Block Chevrolet Severe Duty 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: 1.900”
• Stem Diameter: .3415”
• Installed Height: Stock
• O/A Length: 5.422”
• Tip Length: .250
• Underhead Angle/Radius: 12° x 3/8”
• Margin: .075″
• Seat Width: .085”
• Top Of Head: 7° Dish
• Swirl Polished and Fully Machined
• Chrome Stems and Hard Tips
• XH-428 Stainless Exhaust Material

Benefits

• Superior Stainless for High Temperature Gasoline Engines
• Exhaust Material XH-428 with Double the Ultimate Tensile Strength (at 1500°F) over the competition

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 – Valves

Warranty

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