Valve spring compressor...

Mines a "on head" little puller looking thing. 2 jaws and a jack screw driving 2 sides of hollow ram so you can dig the keepers out.. ditto on the hose clamp around the jaws for safety, I wonder why they dont come with a slip ring that slides down the jaws when set. You can change springs 'on the motor' if you use a clothespin to keep the valve from dropping (or just run the piston to TDC and let it rest on dome.)