Shimmed like I have them they are probably 250 on the seat, not sure what open is but I doubt it is as high as you mention. I lose a lot of lift due to the 59* lifter angle and the offset intake pushrod so they are shimmed up a fair amount to be .050-.060 from coil bind. These springs did two drag weeks and still checked out within spec on seat pressure, did a third with them and retired them for a larger cam and the comp 955 spring that is a little heavier.