[bryanw1968]

Say you're running 8 degrees of initial timing. That would typically not be enough timing at initial. You're truck would fall on its face when you tried to go. When using vacuum advance you should have a hose from your ported vacuum port to the vacuum diaphram on the distributor. That diaphram won't see vacuum until you crack the primary throttle blades thus allowing the diaphram to see vacuum and add timing.

In the distributor you still have to consider the weights and springs to control how much total advance and what RPM it comes in.