school me on dist

if you ran the 9R with 30 total you could have 12* at idle which is pretty close, then your down to springs

To answer your question its what ever more did to make them pass smog.

your correct that you double the number, so a 9R is 18*, if you run 12* initial timing and a 9R (18*) you'll have 30 total mechanical timing. The reason the slot/number is so high is because they pulled the timing way back in the 70's, sometimes even retarded the timing so they still needed a good total timing number