TB42 Timing

Hey all, I ran a timing light on my TB42 carby running on petrol the other weekend and set it to 10 degrees advance, going off what I've read this sounded right? But now I've read that you should set the timing with the vacuum advance disconnected? I'd like to know where is it and how to go about disconnecting it for timing purposes, cheers!

I'm not certain about disconnecting the vacuum advance when setting the timing but if you need to find it, the vacuum advance is the small black hose connected to the distributor.