Just installing New Valve springs Might not be Enough, You Often Need to set Proper Installed Spring Height

you can do this with Machine shop work or you can install Spring Shims  under the springs.

These .040 thick valve spring shims can often add up to 10lbs of valve seat pressure (helps worn out springs also)

This is our most often used shim size in our engine shop  24mm od  17mm id  and .040 thick