Mini flyer,

you make some fair points, nice to see you have a tuned wren!

High tech and accuracy can however sometimes limit cost effectiveness. If the chamber vents are not that critical, i.e. a high tolerance produces little discernible effects, then introducing a jig and accuracy will only slow down the process of manufacture increasing the costs. Perhaps and I am no expert, this is why it is hand done because it is not that critical.

I guess the only way to find out is to test several engines post manufacture under the same stringent basis, and then to play around with the chamber vents.

50lb hammers do have their place in engineering, but I do agree, subtlety is sometimes a better approach!!!

Gazzer