if preload is OK & that is an easy check wheat I'd do is see if I could pinpoint the noisy lifter(s) & dissassemble em then put em back together (keep same innards in same body) as clearances/passages inside are very small & a piece of debris in the oil (#1 reason I like frequent changes) can make it hang up on occaision & I for sure dont care to do a cam breakin procedure for new lifters