It takes a little work to get the 273 adjustable rockers to real performance status. All you need to do is get the good Crane adjusters with the lock nut. You need to face the top of the adjuster holes in the rockers so the nuts will tighten down evenly. Once you do that, they will not back off. With good oiling, those little rockers are good to .600 lift and can take solid roller spring pressures......but the oiling has to be good.
