I. Like using straight manifold vacume the ports on the carburetor that are intended for timing limit the vacume at idle so being more retarded burns more fuel and is a little better for pollution but a retarded idle makes engine run hotter. If you don't have an adjustable vacuum advance pull cap off and make a stop so to limit advance to 40 degrees at idle or cruising
There is a good thread on this but I am on the road try searching vacuum advance.
It explains it better than I can.