Yeah I had one of the pictured ones and used it for about 1 minute until it broke (didn't even get the first spring off) I've since bought the C-clamp type which is also pictured.

ive seen the quick, bad, totally wrong way of doing this, head on table, something supporting valve, ring spanner, on top of spring + HAMMER, then hit spanner, collets go KAPOW, you loose them/chase them around, and off comes the spring, YAY.

That sounds fun!!!

The one in the top picture is for removing the valve spring while the head is still on the block. Loosen the rocker gear off,fill the combustion chamber with commpressed air to stop the valve from falling in to the cylinder. Then you can change the valve stem seals. They dont work all thet well if the head is off the block

There's yet another way I've used succesfully many times on various engines, including A-series.

With head on engine, take out spark plug, rotate to TDC for that cylinder, insert clean rubber tubing, as much as will fit. This will hold the valve in place. Remove rockers from shaft (on some engines, you can leave them on). Use a forked bar with a hole in it to push the spring down, remove the keepers, replace the valve seal (and spring, if that's your goal), then put it back together. The bar I have is basically flat stock turned up on the sides for strength. It's a simple device.

Yeah I broke this one pictured almost straight away....I think that was an assembly defect though....there is a circlip that holds the whole tool together - it just poped off my tool never to be seen again.

I got it replaced this morning at Burson...as Kincrome offer lifetime guarantee on their tools.