I forgot to mention I've had and used a valve spring tester that shows Lbs. and distance when installing valve springs since the mid 1970s, on roller cam springs I shoot for .055 to .080 to coil bind on iron heads and from .065 to .085 on aluminum heads. I try to get the seat pressures within + or- 5 lbs. and shoot for between + or -20 lbs. open pressures by shimming or swapping the inner and outer springs to get what I want