So you disconnect your vacuum advance and set the initial timing, then with springs / weights set the total timing ?
When you reconnect the vacuum advance to a full manifold vacuum you immediately induce advance at idle, so there goes your initial advance up 10º or whatever the vacuum cannister is set at.
As you state "if your static timing is at 10º, at idle it´s actually around 25º with vacuum advance connected" as I see it with the vacuum advance connected it is not static and 25º at idle is way too much.This is why the vacuum advance is disconnected at idle to get a correct static timing reading.
I disagree with the statement of seeing 50º advance if you were going down the highway, (10º initial, 20º - 25º mechanical and 15º from the vacuum) you stated elsewhere when the mechanical advance kicks in the vacuum is not adding anything.
It is also important to get all the advance in before your cruising rpms.
Also if the total timing was set at 34º - 36º how can it get to 50º?
Remember total timing has been restricted to 34º - 36º and even more rpms won´t advance it anymore.
The vacuum advance is an aid to get from idle to mechanical advance and also operates during low engine load when the vacuum is high.
Setting vacuum advance is not measurable it has to be done on the road until pinging is eliminated.
Get yourself a book dedicated to ignitions, I´m going to throw out my computer controlled distributor and go with PORTED vacuum advance, try Ignition Systems by Todd Ryden.
BTW there are several sites in the knowledge base on this.
Last edited by malc; 01-04-2005 at 02:54 AM.