OK, then forget preload suggestion. Were all the rocker adjuster locknuts tight? If so, look for correct clocking on shafts for proper oiling, and make sure oil plugs are in both ends of the shafts. Maybe one plug fell out. If any of those things has happened, pull shaft(s) and check shaft(s) and rocker bore, carefully, for signs of galling. There has to be a reason for bent pushrod. If not a geometry issue, then perhaps a clearance issue: coil bind, retainer to guide/seal, valve to piston, etc.
