Severe Duty / Pro Flo Stainless Steel Exhaust Valves - Set of 8 by Manley Performance
Severe Duty® series valves are Manley's premier product for the performance and racing industry. No other company offers exhaust material XH-428 or intake material NK-844, and no other material demonstrates such a clear advantage over any other. The ultimate tensile strength of XH-428 at 1500°F is nearly twice that of our competitors' EV-8. At 1000°F, Manley NK-844 exhibits an ultimate tensile strength more than four times that of the best competing intake material.
In addition to the superior strength and fatigue characteristics of Manley NK-844, our unique intake material shows an incredible ability to resist chordal fractures. In a high-seal combustion chamber, fuel explosions can actually cause the intake valve to deform and push into the port. The effect of this continuous deformation on competing materials is that a chordal fracture eventually spreads around the valve, quickly turning into a chipped, pie-shaped piece. Manley NK-844 is the absolute best material available to combat disastrous chordal fractures.
Further evidence of the superiority of Manley Severe Duty® valves is evident in our comprehensive fatigue testing. In normal operation without valve float, a valve is subjected to 20,000 to 25,000 lbs of stress. However, when the valve bounces on the seat, the stress immediately rises to 40,000 to 60,000 lbs. Manley exhaust valves (40,000 psi and 1400°F) operated to 100,000,000 (100 million) cycles, while competing products failed at 100,000 cycles. This represents a 1000-fold improvement in fatigue life.
Features
- Head Diameter: 1.590
- Stem Diameter: .3136
- Installed Height: Stock
- O/A Length: 4.923
- Tip Length: .160
- Underhead Angle/Radius: 25° x 7/16°
- Margin: .070
- Seat Width: .115
- Top: 18° Dish
- Weight (grams): 94
- XH-428 Stainless Exhaust Material
- Chrome Stems and Hard Tips
- Swirl Polished and Fully Machined
- O.E. Style Radius Keeper Grooves
Benefits
- Intakes are "Pro Flo" for improved airflow
- Absolute best material choice to combat disastrous chordal fractures
Please note: The images provided are generic and may not accurately represent the product you will receive.
Applications
- 2008–2013 Chevrolet Corvette
- 2010–2015 Chevrolet Camaro SS
- 2009 Pontiac G8 GXP
- 2014–2017 Chevrolet SS
What's in the box?
- 8 - Exhaust Valves
Warranty
- Due to the nature of their intended use, Manley products are sold without warranty.
Before Placing an Order
〇 Regarding Import Consumption Tax
At Shaftoya Shopping Site, we cover the import consumption tax incurred at the time of import, so there will be no additional charges beyond the total amount paid at checkout.
〇 Confirmation of Compatibility
Our entire product database is based on North American (USDM) vehicles. Please verify compatibility with Japanese (JDM) vehicles before placing your order. (If you are unsure if a listed product is compatible with your vehicle, please feel free to contact us. Our support team will be happy to investigate for you.)
If an order is placed without verifying compatibility, we cannot accept returns due to incompatibility.
Please note that even if products are sorted by year, make, and model using the tabs on our homepage, it does not necessarily guarantee fitment on Japanese-market models without modification.
All product information is translated into Japanese using translation software. Due to potential confusing phrasing, please contact us with any questions before ordering.
○ Regarding Shipping
Shipping costs are paid at the time of payment. Estimates for shipping can be automatically calculated by entering your shipping address on the checkout page. For large items like body parts, there may occasionally be a significant discrepancy between the automatically calculated shipping cost and the actual cost. In such cases, we will contact you via email individually.
Basically, all products are shipped internationally from our U.S. warehouse. Unlike domestic Japanese shipping, international delivery takes approximately 7 to 14 days, so please allow ample time for your order. If you are in a hurry, please contact us to check delivery times in advance. All products are shipped via air freight. We do not use sea freight.
○ Regarding Japanese Vehicle Inspection (Shaken) Compatibility
Please note that all products we handle are designed and manufactured outside of Japan. They are not compliant with "Japanese vehicle inspection standards," and we cannot provide documents such as strength calculation reports for Japanese inspections. Therefore, all parts are sold for the purpose of "use on circuits, private property, or off-road," and installation and use are at your own risk.
○ Regarding Warranty
Please check the contents immediately upon arrival. Since all products are shipped internationally from outside of Japan, packaging and products may sustain shipping damage. We only provide returns, refunds, or replacement exchanges for products with shipping damage, defective products, or incorrect items if you contact us within 7 days of receipt. Please understand that for products sold through us, warranty support will be handled "exclusively through us." We do not provide support through other companies or agencies located within Japan.