How do I replace this radiator air valve?

Many of the radiator air valves in the house I just purchased are noisy (steam heat). I've been going around simply unscrewing the old ones and screwing in new ones. Things are getting quieter.

However there's one baseboard radiator where I'm not sure how to remove the valve. It doesn't seem to turn at all, and even if it did, the wall would be in the way. I attached some pictures for reference.

What's the right way to go about this?

 

Is this the only cast iron baseboard radiation installed in your house or is the whole heating system this type of radiation? For this one, you will have to break the union on the inlet pipe , remove the screws holding the rad to the wall and pulling the rad towards you enough to spin the vent. Just a note, cast iron baseboard radiation should not be used in a 1 pipe steam system Normally, if I were replacing standing cast iron radiators I would use 1-1/4" or 2" all steel baseboard radiation. A friend of mine bought a large house in central Pennsylvania where a contractor removed all the free standing cast iron radiators and installed cast iron baseboard radiation. Now, the heating system does not work and he is left with a cold house. .

 

T,
Loosening or removing cast iron baseboard can be a problem, especially if you've never done it before.

Since you're changing the vent anyway my suggestion would be to leave the unit in place and snap of the vent and then remove the nut which will come out with the right tool. Put a pipe on your wrench to give you more leverage. If you have a big problem you can remove the whole bushing and then replace with a physically smaller vent like the VARIVALVE steam vent.

They come angle or straight to fit your project. The sight below will show you some options.

https://www.supplyhouse.com/Steam-Vents-27901000

https://www.supplyhouse.com/Varivalv...alve-3840000-p

https://www.supplyhouse.com/Varivalv...alve-3841000-p

Hope this helps a little.

 

Looks like one copper pipe supplying it.
You may be able to carefully slide the radiator away from the wall on the vent side.