Ported or manifold Vacuum to Dist.

For example, if the timing measured indicates the distributor has long primary advance, intended for an initial timing of 0 or -5* then using manifold vac would worth trying. OTH if the timing shows a curve where initial can be set at 10 to 15*BTC around 600 - 700 rpm, and timing end up in the 30- 35* range around 3000 - 4000 rpm, then ported is fine.

All testing done with the vacuum advance hose plugged of course.