The carby and vac hoses together compose about 10 different systems, any of which could be your problem.
If you have no knowledge of all the different systems, you can buy a can of 'stuff' to spray in every dirrection and it may work. Try carby cleaner as a start, then move through your Dads collection, but stop short of painting it red.
Replace any vac hose that is cracked. Block off any vac hose that goes no where.
Replace the points.