If you are talking about the factory adjustable rockers, they are self locking. Once they get loose, they are worn out.
Take a tap and run it through the adjuster holes to remove any self locking resistance, then get the good Crane adjusters with lock nuts and replace the crappy factory ones. You will have to dress the tops of the adjuster holes on the rockers so the nuts will fit and lock down tight, but it's an easy job.