Once you get the engine running, the ******* valve adjustment never fails. You idle engine, back rocker nut off until clatter occurs. Tighten nut until clatter stops. Tighten nut 1/8 to 1/4 turn more. That rocker is adjusted. Move to next rocker.
After each rocker adjustment, stop engine and lock the nut in place. Start engine and do the next rocker.