rskrause

I think this was partially explained in another post, but just to make it clear: the amount of lift a given spring can handle depends largely on the installed height. Obviously, the maximum cannot exceed the distance between the top of the valve guide and the retainer. But assuming that's not an issue the next variable to consider after installed height is coil bind. This is listed in the specs for each spring. I think it's 1.150" for the 987. Obviously, exceed this and something will break. Addtional clearance is needed though, most people use 0.050-0.060". So, assuming no retainer to valve guide or rocker to retainer issues, the max lift is the installed height - (coil bind+0.060").

Example: I am using the 987 spring installed at 1.850". Coil bind is 1.150". So the max lift is 0.640". Setup at the more typical 1.850" installed height gives 0.590" max lift. The new #987 springs measured out at ~115psi seat pressure when installed on my heads at 1.850". Springs lose ~10% of their pressure on break in, so I will be left with ~105psi, quite adequate for the ~6,200rpm redline I use. Higher rpm will require more seat and open presure.

All of the max lift figures in the Comp Cams catalog are conservative, most seem to be ~0.100" less than the spring can actually handle. I don't know why they do this.

Rich Krause

PoorMan

thxs, that makes alittle more sense

Jeff D