Ok, how I do it......
First, I make an educated guess where the total and initial need to be.
For my last build I figured 18 initial and 32 total. In my case, it's a good baseline, prior to testing. The small amount of advance is due to my BBM heads, which have a faster burn chamber.
Here is the regular slot,
So, being I use a Duraspark, I weld up the advance slot.
I then use a grinding wheel to cut a little slot, then I clean it up with a die grinder carbide bit and some sandrolls.
Since I was only looking for a little advance, I ground a small slot to start with.
.300 or .350 I forget
Plug vac advance at this time.
I install the springs I think I might need to get the advance in when needed. Things to consider, vehicle weight, gearing, convertor, etc. Think about how loaded the engine must be to get things rolling. In my case I have a loose convertor and didn't see the need for the advance to come in too soon, so I aim for 2800rpms. My car cruises around there so I figure it's a good starting point. Plus with a duraspark you can bend the tab for final adjustment.
I then install the distributor and fire the engine up.
First thing I'm looking for is how the vehicle idles at the initial advance. Hot start should also be a consideration, tho with a mini starter, I was pretty certain I could go a little either way.
idles at 18 just fine, maybe it likes 20, maybe it prefers 16. Figure it out.
Once I have that number pegged. I get the total to be where I want to be. Go for a drive. Think you need more? add more, think you need less, add less. Want it to come in sooner, make it so. I don't worry about initial at this time.
Once I get a good idea of my total, I take the distributor apart and reweld or grind (it's easier to grind) to get my initial where I want and total where I want.
Sometimes with me, this takes 3-4 times of reinstalling/taking apart (I do it on the engine) to get it all perfect.
At this time, in order to figure and get a baseline for vacuum advance I run the engine. Vac advance isn't plugged, it's attached to my handheld vacuum pump.
At max advance/cruise rpm I use my vacuum pump to bring the advance in as needed. If I need to change what I see for a baseline I do so.
Once again, hook everything up and go for a ride. like it? don't like it? make adjustments.
Hope that was a little more specific than my last post.
and sure, there are better ways to do with with a distributor machine.... but I don't have one.
Good luck
Drew