Chevrolet Repair: hydraulic lifters, hydraulic lifters, oily mess

Question
i have a 1972 396 opened to 402ci with hyd lifters just started hearing a tap in one of the valves. is there a way to adjust?  this engine is in a restored 67 chevelle convt. i hate to make an oily mess under the hood any suggestions thanks mike

Answer
Well, hopefully without any mechanical damage, such as cam going flat, or rocker arm failure, or "sticky lifter", remove valve cover of noisey side, locate "loose" rocker, If exhaust, turn engine to where int. is open, while spining pushrod with fingers, turn nut down until you just feel pressure on pushrod, turn nut 1/2 turn more, nut should have some resistance turning(self locking nut), if int., turn engine until exh. is just starting to open, adjust with same method. Replace V.C., start eng., Done! If same rocker loosens again, either cam is going flat, or nut has failed! Good Luck!