LS Engine Valve Springs. PAC 1905 Dual Spring kit. Features a PAC 1905 dual spring (x16), Kelford Titanium retainer (x16), steel locator spring base (x16) and Viton stem seal (x16). PAC 1905 is best suited to a high performance street or mild motorsport LS V8 engine. For high performance motorsport engines Kelford recommends PAC 1204X.160lb at 1.800" installed height. 425lb at 1.125". Coil bind 1.020".