Radiator shutoff packing

[imaddicted2u]

I cut the old leaky coal boiler out of the system over the summer. It was piped in parallel with the oil fired boiler. Since cutting out the coal boiler I've had to close some of the rad valves as the rooms closest to the boiler were getting too hot. After removing the paint and getting this one valve to close it started leaking like crazy. There were no threads left to tighten the packing nut. What should I use to replace the packing? What's in there now looks like a graphite disc. I can get 1/8" graphite twist packing at the local hardware store. Can that be safely used fill the void and create a proper seal or would something else be better suited to the task?
1/8" graphite twist packing

 

[imaddicted2u]

I ended up using PTFE impregnated string, Wrapped the stem, filled the packing area and compressed it by tightening the packing nut. Did that a few times until it wouldn't hold anymore. Leak gone and lots of room to take up the packing, if necessary.

 

[WC1]

Well done. Most gland nuts respond well to the treatment