340,
What is important to remember is that the engine will:
- idle best [ smoothest, highest rpm, highest vacuum ]
- use less fuel
- run cooler
- be most efficient
when it has a LOT of timing at idle.......more than the 10-12* the engine had on the showroom floor.
The actual amount will vary engine to engine, mainly dependant on cam duration/overlap & CR to a lesser extent. Some engines will need as much as 50*. MVA is
one method of obtaining the reqd idle timing; it is used a lot because it is simple to hook up: effective, adjustable, reliable & load sensitive. Load sensitive is good, because under load the timing drops way. Using locked timing gives the reqd idle timing, but is there all the time, & does not drop off with load. When I hear comments like 'MVA' didn't work for me, 90% of the time it wasn't set up right. Then MVA gets the blame....
Good move getting a dist with VA. Make sure it is adjustable; it will have the hexagon end on the VA unit.
I could give you lots of good MVA stories, here is one....
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