My older brother and I both have the old Crane aluminum rockers and we were racing pretty regular there for a while. Both of us have J heads and both running the .509 - 292 Direct Connection camshaft. We bought a 1.5 ratio set and a 1.6 ratio set and each of us has 1.5s on the intake and 1.6s on the exhaust. Neither of us are running any super high spring pressures though but we've never had an issue with the non bushed aluminum Crane rockers.