This custom valve spring kit goes far beyond typical “performance” BMW spring kits. Rather than double springs or springs that are much too stiff, resulting in increased resistance and wear, our springs are an engineered solution.
Designed for use with the Sunbelt SportCams, this kit was engineered with extensive Spintron testing. This ensures the springs apply the correct amount of pressure to keep the valves in contact with the cam lobes without any unnecessary brute force (seat pressure) that may cause parasitic losses, wear, and fatigue. This kit will allow the valvetrain to rev to 9,500 RPM’s with Sunbelt cams, but most engines will be bottom-end rev limited well below this level. For most engines with stock based rotating assemblies we suggest a non-sustained maximum limit of 7,400 for 3L and 7,200 for 3.2L engines.
Kit includes valve springs, locaters, and retainers. Fits all 1992-2000 M50 engine based cars, including 323, 325, 328, M3, and Z3.