The BTR platinum spring kit would be inducted into the LS aftermarket hall of fame if such a thing existed. Whether you’re putting together a daily driver with a mild cam, a 600 hp N/A stroker, or a turbocharged 1000 hp brawler, our platinum spring kit will make sure your valves are right where your cam wants them to be at all times. They are designed to be used with stock rocker arms. This is a drop-in kit for 15° LS heads. It will also work with LS7 heads when used with a .045” shim (Part numbers SS015 +SS030). This kit will not fit LS9 engines. Spring specs are as follows: 155 lbs @ 1.780" 380 lbs @ 1.180" 400 lbs @ 1.130" Coil bind @ 1.100"