[69 longhorn]

I ran several sets of Z-28 springs,with cams in the 460-480 range on valve lift(on the older 'fuelie" heads).....no trouble. It definately sounds like something is binding,whether it be coil bind due to improper installed height,retainer to guide interferance,Or possibly rocker to stud interferance........its hard to say. You do need a long slot rocker when into & past the .450 lift range,& as posted the rockers are self aligning for the Vortecs. Good luck.......69