With the use of an easily-made special tool, these pre-war staples are simple to put on.
1: Hairpin valve springs keep the coil away from the heat and are easily changed when tired or broken; but better steels and demand for enclosed valve gear post-war saw them fade from use.
2: They can be changed individually without disturbing the valve, but to compress for fitting you need a special tool. I made this one from scrap; I carry it in the toolbox with a spare spring.
3: You can replace these springs one side at a time. The taper fit of the collar/collets is sound enough for the collar not to tip over from the pressure of one spring while you work on the other side.
4: Now slide the compressed spring into the corresponding holes in the valve guide until the loop of the spring hooks under the lip of the valve collar, release the compressor and you’re there.