The link below is a pdf of a old but good book on tuning SU carbs.
Its a great thing to print off and keep with the car
Also at the back it has a guide on what set up the carbs were done at the factory… note the spring colour! - and here is the XK bit…
Hope its helps folk
Regards
Marc
http://mgaguru.com/mgtech/books/pdf/Tuning_SU_Carburetors.pdf