What year of Mamod intermixed drain plug boilers and sight glass fireboxes?
I was looking for a parts TE, but this sad SR followed me home.
On a previous project, I tried the approach of cutting off the whistle but that met with failure. Which also cost me a whistle. I ended up putting a different boiler in it since the brass got too bent up.
This time, I went with the end cap removal. I drilled a hole to make a handle the heated with a torch until I could pop it off. Then I resoldered the bush from the inside. I noticed the previous solder was super thin.
I also put extra around the pressure valve bush.
I also solder in the screws instead of rivets and seal in the little hole with a soldered brass bolt.
The old whistle was not harmed.

After I soldered in the screws then used solder paste for the cap as well as a ring of solder inside. I think paste is the way to go for the cap. I don't hear anything rattling so the ring of solder must have melted

Also the boiler passed the pressure test.