What makes the XH-428 and NK-844 materials special?

These are advanced materials chosen for their exceptional strength at high temperatures. XH-428 for exhaust valves offers nearly double the tensile strength at 1500°F compared to common alternatives, while NK-844 for intake valves provides over four times the tensile strength at 1000°F.

How do the swirl-polished and machined faces benefit my engine?

The swirl-polished areas under the head help guide airflow more smoothly into the cylinder. The fully machined combustion faces ensure a clean seal and contribute to more efficient combustion, which can help optimize engine performance.

Are these valves suitable for everyday street use or just racing?

Manley's Severe Duty valves are designed for high-temperature gasoline engines and have proven fatigue life, making them suitable for demanding applications including racing and high-performance street use where engine temperatures can be elevated.

Specifications

Brand: Manley Performance
Part #: 11805-8
UPC: 807298052892

Manley Ford 351C 1.710 Inch Head Diameter / .3415 Inch Stem / Diameter Stock Height ( Set of 8)

Name: Manley Ford 351C 1.710 Inch Head Diameter / .3415 Inch Stem / Diameter Stock Height ( Set of 8)
Brand: Manley Performance
SKU: manley-performance-manley-ford-351c-1-710-inch-head-diameter-3415-inch-stem-diam-t14-211835
Price: 349.40 USD
Availability: BackOrder

$349.40

On Backorder

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Manley Severe Duty valves for Ford 351C. XH-428 exhaust material for high temps. Set of 8.

Key Features

Set of 8 Manley Severe Duty valves for Ford 351C engines.
Exhaust valves are made from XH-428 material, offering high tensile strength at 1500°F.
Intake valves are made from NK-844 material, with over four times the ultimate tensile strength of competing intake valve materials at 1000°F.
These valves have undergone rigorous fatigue testing, enduring up to 100 million cycles at 40,000 psi and 1400°F.
Features chrome stems and hard tips for enhanced durability and longevity.
Swirl polished under head areas and fully machined combustion faces help improve airflow and combustion efficiency.

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About this part

Product Details

Starting with XH-428 material for the exhaust valves, Manley's Severe Duty valves are built for demanding high-temperature gasoline engines. These valves are designed to handle extreme stress, enduring up to 100 million cycles in fatigue tests at 40,000 psi and 1400°F, which is significantly longer than many competitor parts. The intake valves use NK-844 material, offering superior tensile strength at high temperatures compared to other options.

Beyond the advanced materials, these valves feature chrome stems and hard tips for added durability and longevity. The under-head areas are swirl polished to help improve airflow, and the combustion faces are fully machined for better combustion efficiency. This set includes eight valves, each with a 1.710-inch head diameter, a .3415-inch stem diameter, and stock height, making them a solid choice for rebuilding or upgrading your Ford 351C engine.