Late reply from OzStick added to archive:
--------
I'm doing as suggested and scouring the entire forum to find answers to all my modding questions, when I stumbled over this thread which appeared to cause a bit of debate.
Ox!gen suggested there is only vacuum advance capability on the Cordia dizzy, however Grumbly recalled a write up done by someone in Adelaide on regraphing the Cordia dizzy which explained it has both advance and retard on it.
I remembered reading a magazine article showing exactly that, which I managed to find. It is from the first edition of a magazine called Hardcore Performance and the article is called Graphing A Spark.
It follows the process involved in regraphing the standard Cordia dizzy as done by "Local Adelaide tuner Peter Hall" to cater for an engine outputting at least 20% more power than standard.
The article quotes the following:
The distributor responds to both vacuum and boost courtesy of a simple external diaphragm canister (vacuum advance/boost retard unit) that bolts onto the outside of the distributor body. The advance/retard unit has a manifold pressure pickup on the outside of it that hooks directly to the plenum chamber to sense vacuum or boost.
A movable rod that is directly attached to the distributor baseplate can either push it in to retard or pull it into an advance condition.
It's a really interesting article and food for thought for those tossing up the idea of aftermarket management ie going MPI & how to handle ignition.
If you're interested in a copy of the article let me know here and if enough people are keen I will scan it into a file and drop it onto the web (if it's not too large!) for anyone to download.
----
Thanks