A previous shop installed bronze helical type screw in guide liners and positive stem seals, but didn't top off the guides for the difference in seal height. All of the stem seals were smashed by the retainers because the only available cam is a higher lift &quot;RV&quot; type with .500+ lift. They obviously didn't check for proper clearance. The factory guides are replaceable, so Tuf-Enuf installed the solid bronze type guides.