Important to make sure the join under the front carby is airtight, or the vacuum won't work and the carbies can't be tuned properly. Early cars had a brass adapter screwed into the carby body which must be fitted first and made tight. The tiny fibre sealing washer is usually long gone. Then a nut and olive on the vacuum tube attaches the tube to the brass adaptor. Later cars had a push on carby fitting which is a better way to go. Early dizzy canisters had a thread fitting for the vacuum tube - later were push-on.
Check the dizzy vacuum canister is operating - gas vapours can harden the diaphragm so it can't flex, rendering it useless. The vacuum advance only helps with better gas mileage at highway speed, so isn't vital. If it's removed the hole under the front carby must be plugged.
Viv