My doomed 408 build

need much more info: what kind of oil pressure are you running? Are you POSITIVE ALL the oil gallery plugs are installed? What kind of oil are you using? Is this LA or Magnum? Have you searched archives for threads on proper rocker geometry? Also, there can be problems with insufficient retainer to guide (and seal) clearance in addition to coil-bind. All the aforementioned problems (and probably some more i failed to mention) are fairly common in builds by "non-Mopar fluent" engine builders.