I recently posted a question here about what influence adjusting the offset of the spring perches (or spring posts, whatever is correct) on my '77 distributor would have on the timing curves, but did not get much relevant feedback. Here is the link to that thread with pics. So I'll do some testing.
I think repeated adjustment of the perches from above, is very difficult without ruining the perches, it seems like it is easy to chip off metal pieces, and in the end they will just be rounded off. On the other hand the distributor may stay in place, and the engine turned by hand until the perches are visible.
I opted to make a hole from the underside of the distributor body instead, by enlarging the ventilation hole. The ventilation hole is not absolutely in line with the nuts, so I drilled an undersized hole and carefully enlarged it with a rotating file. The best would of course have been to do a precision drilling in a drill press, but I don't have one here.
I once had a clockmaker's socket set from 1-12 mm, spaced in .5 mm. The 8.5 mm would have been the perfect size, but some #%¤& stole it from me a long time ago. The closest I came in finding a socket for the nut, is 11/32". It cost a fortune, and of course, the next day I found a tiny 11/32" socket in a tool kit I got for X-mas as a kid, I just forgot I still had it! I am making a handle for the little socket, so the nuts can be turned from the underside without having to remove the distributor from the engine, even if it will be difficult. There is not much space there. To get any accuracy when adjusting, the best solution will be to remove the distributor each time anyway.
The hole will normally be covered with an aluminum lid with a replacement ventilation hole in it, and fastened with a screw. The threaded hole for the screw is there, but my camera's lack of focus override makes it hard to see the threads.
The goods in the distributor housing is not very thick, and the distance from the floor up to the nut is very limited, otherwise the use of a threaded plug would have been an alternative.
I have the spring kit from bigslant6fan, and also a MP kit for their V8 distributor, plus an assortment of springs of unknown origin. For now, I'll just see if my current choice of springs is good, one green spring from bigslant6fan's kit, and one long-loop spring from a 318 to dampen the final movement to avoid bouncing when the weights reach the end of the slots in the governor. The governor is a #9. The testing will continue through the summer, and I'll report back on my findings.
Olaf.
