For specialised race use only, these springs are 267lb@ 1/2"lift fitted. (use VSU-100 for race and fast road cams) Modern high lift, short duration camshafts have posed quite a few problems for the general public in recent years. Widely available performance valve springs were outdated overnight, as it became necessary to reduce spring crush. This, in turn, caused low valve seat pressures creating valve float at high rpm. Manufactured from super quality silicone wire imported from Switzerland, their resistance against fading and breaking is extremely high. They are also designed to take standard type top caps. They can be fitted directly to the head with no fear of spring crush. 280lb Dual springs for race use up to 8000 rpm and .570 lift. The standard fitted length of springs is 1.4" - 1.42". Spacer shims are available to increase valve seat poundage and overall spring rate. If the spring or valve seats in the head have already been machined, it will be necessary to re-shim to the correct fitted length.The bottom collars for the inner springs are No Longer Required when using our range of silicone wire
springs as they are a slight interferance fit and friction damped.