For valvesprings, KT Engines chose a nested spring design from Comp Cams. Installed in these heads, they rate out at 120 pounds on the seat and approximately 400 over the nose. The Kimmel Street Stock series limits rpms to 5,000, so nothing too stout is necessary. In this photo you can also see that the inner springs have been left out. This is to lighten the spring pressure for breaking in the flat tappet camshaft. After the cam is broken in, the full spring package will be installed.