What makes these valves 'Severe Duty'?

The 'Severe Duty' designation comes from the advanced materials used, like NK-844 for intake valves, and the rigorous fatigue testing they undergo. They are built to withstand higher stress and more cycles than standard valves, especially in high-temperature engine conditions.

What is the benefit of swirl polished under head areas?

Swirl polishing the area under the valve head helps to smooth the airflow as it enters the combustion chamber. This can lead to improved volumetric efficiency and better overall combustion performance in the engine.

Does this kit include exhaust valves?

No, this kit (part number 12854-8) is specifically for intake valves. Manley also offers separate Severe Duty exhaust valves made from XH-428 material for Chevrolet Big Block engines.

Specifications

Brand: Manley Performance
Part #: 12854-8
UPC: 807298105161

Manley Chevrolet Big Block 2.300 Head Dia .5.494in Stem Severe Duty Intake Valve Kit - Set of 8

Name: Manley Chevrolet Big Block 2.300 Head Dia .5.494in Stem Severe Duty Intake Valve Kit - Set of 8
Brand: Manley Performance
SKU: manley-performance-manley-chevrolet-big-block-2-300-head-dia-5-494in-stem-severe-t14-718266
Price: 361.47 USD
Availability: BackOrder

$361.47

On Backorder

Order now to reserve yours — we'll ship as soon as stock arrives. Full refund if we're unable to fulfill.

Manley Severe Duty Intake Valve Kit for Chevrolet Big Block. Made from NK-844 material for improved high-temperature strength.

Key Features

This is a set of 8 intake valves for Chevrolet Big Block engines.
Intake valves are constructed from NK-844 material for improved high-temperature tensile strength.
Features a 2.300-inch head diameter and a 5.494-inch stem length.
Chrome stems and hard tips are included for enhanced durability.
Swirl polished under head areas and fully machined combustion faces help improve airflow and combustion efficiency.
Designed for high-temperature gasoline engines.

⚠️ CA WARNING: This product can expose you to chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm. Learn more

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About this part

Product Details

These Manley Severe Duty intake valves are made from NK-844 material, which offers over four times the ultimate tensile strength of typical intake valve materials at 1000°F. This makes them a solid choice for high-temperature gasoline engines, especially those built for performance or racing applications. The valves feature a 2.300-inch head diameter and a 5.494-inch stem length, designed to fit Chevrolet Big Block engines.

Beyond the advanced material, these valves incorporate chrome stems and hard tips to improve their durability and lifespan under demanding conditions. The under-head areas are swirl polished to help with airflow into the combustion chamber, and the combustion faces are fully machined for better efficiency. Manley has put these valves through rigorous fatigue testing, showing they can withstand significantly more cycles than many competitor valves, even at high temperatures and stress levels.

This kit includes a set of 8 intake valves, providing a complete solution for rebuilding or upgrading your engine's cylinder heads. If you're working on a performance build for your Chevrolet Big Block, these valves are built to handle the heat and stress.