I have seen in the past on 4 groove valves where the keepers have worn into the grooves....... severely........ which can allow the retainer to ride higher on the valve.
I’ve also seen where the 2 groove vs 4 groove valves will have the retainers sitting at different heights.
Some SB heads use all 4 groove valves, some have 2 groove intakes/4 groove exhausts.
Some of the replacement 4 groove exhaust valves have thinner grooves, which don’t allow the keepers to seat as deeply into the groove...... which can lower the retainer relative to the valve tip.
