The quickest, easiest way to remove valve springs with the heads on the engine.  Just remove the rocker arm, put this tool in its place and using a 3/8" drive ratchet, pull the tool down on the retainer and remove the valve locks (keepers).  The low profile works great for getting to the back of the engine on F-body cars.  You will, of course, need to pressurize the cylinder to keep the valves from dropping, and the easiest way to do that is with our cylinder pressure tool.