Manley Chevrolet Small Block Exhaust Valve Kit - 1.625in Head Dia. 5.365in O/A Length, 0.3415in Stem

Starting with XH-428 material for the exhaust valves, Manley Performance builds these Severe Duty? valves to handle serious stress. These are designed for Chevrolet Small Block engines, specifically for the exhaust side, featuring a 1.625-inch head diameter and a 5.365-inch overall length with a 0.3415-inch stem diameter. This specific material choice is notable because it offers nearly double the ultimate tensile strength at high temperatures compared to common competitor materials like EV-8, making it a strong option for demanding applications.

Beyond the material, these valves incorporate chrome stems and hard tips, which adds to their overall durability and lifespan. The under-head areas are swirl-polished to help improve airflow into the cylinder, and the combustion faces are fully machined to promote better combustion efficiency. Manley has put these valves through rigorous fatigue testing, enduring up to 100 million cycles at high stress and temperature levels, far outperforming many competitor valves that failed much sooner. This level of testing and material science means you're getting a well-built part designed for longevity under tough conditions.

While these are exhaust valves, Manley also uses their NK-844 material for the intake valves in their Severe Duty? line, which boasts significantly higher tensile strength than competing intake valve materials. If you're rebuilding the top end of a high-temperature gasoline engine and need parts that can withstand extreme cycles and heat, these Manley valves are a solid option.