The holes at the bottom of the Prechamber are not not so big and the Prechamber could be stuffed with Toilet Paper to prevent things from falling inside.
If the threads on you Tool Are stripped it might be a bad idea to try.

Was your Prechamber Tool a Real one of was it one of Mercedes resourses Bicycle Hub Pullers? Or a Homemade Tool made from a Bicycle Hub Puller?

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84 300D, 82 Volvo 244Gl Diesel

It worked on an undamaged prechamber on my 300k miles merc. I wanted one of those bicycle hub pullers because they were cheap. It was from baum tool and came with a slide hammer. The threads on the tool are bad enough that I would never use on a good prechamber, but their still pretty good. Its the prechamber itself that is mangled.

I am holding off on doing anything today (50 minute round trip to get to the car). Do you think I should reuse my home made chaser to get the threads in the best possible shape? I could try to acquire a tap, but my thinking is that might be worse at this stage. Use something better than JBweld. I stupidly have used the quick version in the past and was not impressed.
Things better than JB weld:
1. "autobody panel adhesive"
2. Loctite 324 industrial adhesive $20 for a small bottle and another $30 for the Loctite 7075 spray activator
3. Couple of spots of 3M 4200 UV cure to hold while a nice bead of 3m 5200 sets, maybe $12 a tube each (urethane). Urethane is used to join body parts in production, and it is generally more flexible than epoxy. I have heard than urethane glued body joints can be stronger than the steel they join.
4. Based on my experience of fixing stuff that seemed nearly hopeless, I would recommend PC7

I am leaning to the 3M 5200 because its got some flex and might be less likely to break with slide hammering? (what do I know). 7 days to set though! Suggestions anyone.