Originally Posted by 454C10
First thing to do is pull out one of the old springs and retainers.
Then put the new retainer and lock on the valve (with out the spring). And measure from the bottom of the retainer to the spring cup with the valve closed. If the installed height is too much then add some shims, if not enough then it will need some machine work to lower the spring cups.
Then measure how far the retainer will go down before hitting the oil seal. There should at least 0.060" clearance between the seal and the retainer at max lift.
Then measure the spring pressure at the installed height and at max lift. Also make sure it will not stack at the max valve lift. Give at least 0.080" clearance between spring stack and max valve lift.
Yea, I'm familiar with the process (but thanks for the info). What I'm asking is how likely it is that I'll need to shim or machine. Thing is, I'm in England and even the spring shims are hard to come by without ordering them from over there and waiting 2-3 weeks for them to arrive. How likely is it that I can just install the Comp springs/locks/retainers and be right at the recommended installed height right off the bat? Tempted just to stick my old (but refaced, pressure-tested and hot-tanked) O.E. heads back on.