Now that I'm closing in on the dwell questio, thanks to BBs first responders, I'm felling like maybe I'll try adjusting the SUs. Mine are HS6.

I have a synchronizer that I got in 20006 and yet to use. Actually thinking about getting another one so I don't have to switch it back and forth. I also have my SU wrench for the jet adjusting nut that came with my MGTD back in 1966, been holding on to it just in case I'd ever need it again.

I also have a photo copy of the shop manual, a copy of "SU Carburetters Tuning Tips & Techniques", the yellow Chilton's yellow, hard cover Volvo Repair and tune up guide, plus some other reference materials and many saved BB threads on the subject.

Too much information! For instance, one resource suggests that I loosen the nuts that tighten the throttle spindle connectors and like wise jet control interconnection
before attempting adjustment of idle etc. That makes the most sense to me although another resource has them loosened and retightened before the adjustments are complete. Which is it?