retard timing mechanically?

Bakerlite said
Build or pay... the option is up to you. Personally I like to build stuff.
You can also just hook your vac advance to the vac side of your intake manifold. Under vac (ie no boost) it will advance timing to whatever base timing you want and under boost it will retard it. Cost is $0...
This is what I will be using on my turbo build.
Click to expand...
The only thing I can't build are parts that need welded. I can piece stuff together as long as it don't need welded.
But the big "$0" sparked my interest so all you do is run it to the manifold? I understand there isn't any vacuum in the intake at wot, so that keeps timing retarded enuff?
What is a good base timing?