I need to take the valve springs out of my cossie head what tool do I need to do this

 

Valve spring compressor

 

If head is on the table off the engine then you just need hammer and right size socket. Place socket over the retainer and give a punch with the hammer, cotters should fly somewhere around the garage. Ofcourse this doesn't work when you are assembling the head back together

 

And when you can't find them your fucked as they are a pain to get hold of!!
Valve spring compressor as said, if you wanted to do it on the car there is a tool you can use to do it but never actually used one myself so don't know the name of it