I am in the process of stripping down and ‘re building a couple of HIF4 carburettors – AUD616 model which has the built in vac port for the distributor advance.
The information from the “official” SU Carb site – link below – is invaluable.
It details the dismantling, inspection, assembly and tuning of the carbs.
http://sucarb.co.uk/technical-carburetter-maintenance-settings-hif
I am also replacing the emissions throttle plate with a plain throttle plate – supposed to improve performance.