SB rockers hitting springs and retainers

Lay a straight edge across the top od the valve tips to see if they are all the same length. I had a set of 440 heads done at a local shop years ago, they didn't cut the valves to the correct length after grinding them. When it warmed up there was a pop in the intake, I found that some of the valves being held open because the installed height was wrong. There is a spec for valve length measuring from the spring seat to the valve tip.