What makes these valves 'Severe Duty'?

The 'Severe Duty' designation comes from the use of XH-428 material, which offers significantly higher tensile strength at high temperatures. They are also rigorously tested for fatigue life, enduring millions of cycles under extreme stress and heat compared to standard valves.

What is the benefit of swirl-polished under-head areas?

Swirl polishing the area under the valve head helps to improve airflow dynamics as the air and fuel mixture enters the combustion chamber. This can contribute to more efficient combustion and potentially better engine performance.

Are these valves sold individually or as a set?

This product is a set of 8 exhaust valves, suitable for most V8 engines like the Chevy LS-1 and LS-2 small block applications.

Specifications

Brand: Manley Performance
Part #: 11673-8
UPC: 807298051437

Manley Chevy LS-1, LS-2 Small Block 1.550 Pro Flo Severe Duty Exhaust Valves (Set of 8)

Name: Manley Chevy LS-1, LS-2 Small Block 1.550 Pro Flo Severe Duty Exhaust Valves (Set of 8)
Brand: Manley Performance
SKU: manley-performance-manley-chevy-ls-1-ls-2-small-block-1-550-pro-flo-severe-duty--t14-4337396
Price: 349.40 USD
Availability: BackOrder

$349.40

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Manley Chevy LS-1, LS-2 Small Block 1.550 Pro Flo Severe Duty Exhaust Valves (Set of 8). Built with XH-428 material for extreme durability.

Key Features

Fits Chevy LS-1 and LS-2 Small Block engines.
Set includes 8 exhaust valves.
Constructed from XH-428 material for high-temperature strength.
Features a 1.550-inch head diameter and .3136-inch stem diameter.
Chrome stems and hard tips add to durability.
Swirl-polished under-head areas and machined combustion faces improve airflow.

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About this part

Product Details

Manley's Pro Flo Severe Duty exhaust valves are built from XH-428 material, a choice that offers nearly double the ultimate tensile strength at 1500°F compared to common EV-8 materials. This makes them a solid option for high-temperature gasoline engines, especially those in performance applications where valves face extreme stress. The valves have a 1.550-inch head diameter and a .3136-inch stem diameter, with an overall length of 4.923 inches.

These valves are designed for improved airflow and combustion efficiency, featuring swirl-polished under-head areas and fully machined combustion faces. They also incorporate chrome stems and hard tips to further enhance their durability and longevity. Rigorous fatigue testing shows these valves can endure up to 100 million cycles at 40,000 psi and 1400°F, a notable improvement over competitor parts that often fail after only 100,000 cycles.