I always run the damper spring. Supposed to help with harmonics. I did test pressures with and without damper though at some point. IIRC w/o looking, it wasn't much different w or w/o damper. What I always check carefully is valvelock or retainer (whatever is hanging lower) and valve seal clearance. Pretty tight with .500+" camshafts. It helps considerably if you can order valves with groove lock cut around .315 to .330 instead of factory .360-.370". That also helps to easily get spring heights around 1.700+" and helps out with lower closed pressure. Haven't yet found +.050 LS retainers or +.050 stamped 5/16" valve locks. I literally have 1700 -.060 stamped hardened keepers. Easy to identify by their green color. Enough for 200+ heads! Enough for a few lifetimes... Anyone need any? Hehe.
Todd