My instructions does`nt mention any reduction or increase of vacume by adjusting it.
What it does mention is [turn allen wrench (180 degrees) clockwise to reduce vacume advance by aproximately 2 to 3 degrees]. That`s advance, not Hg or " of vacume
Right, it doesn't say that specifically - I'm deducing based on the section on tuning for maximum performance. It makes sense when you consider you're simply adjusting spring pressure against the diaphragm. I've confirmed this using a Mityvac.
With mine turned all the way in (fully clockwise), it takes a minimum of 10" of vacuum to start to actuate it. As I back it out, that number goes up. And 1 full turn seems to coincide with an inch of vacuum. Makes sense that I can add or subtract vacuum advance by adjusting spring pressure. Despite how the instructions are worded (with number of turns coinciding with an increase or reduction of timing degrees), I found that turning the adjustment clockwise reduces the amount of vacuum required to move it. Turning it counterclockwise increases the amount of vacuum required to move it (from 0*).
