These 90# springs are OEM GM LS6 springs. The LS6 engine comes from the factory with .550" of lift and spins to 6500 RPM to give an idea of what these springs were made for with factory reliability. The seat pressure is lower than the Comp Cams 105# springs but the spring rate is higher so they do work well for more aggressive ramp rates. Their springs work well with the VS and NIC cams when shifting at 6000 rpm.
Why install valve springs?
When boost is increased, that boost is pushing on the back side of the intake valves, therefore your actual valve spring pressure is reduced. So when you add valve springs it allows you to rev higher and increase your boost without losing any performance to valve float. If you are boosted and want to shift above 6000rpms, then we would recommend the Comp Cams 136# or Crow 130# valve springs instead.
1.80 recommended install height.
These are all packaged in sets of 16.