He was close. Instead of water, use mercury.
The number represents the vacuum in inches of Mercury when the advance starts,
the vacuum in inches of Mercury when the advance stops and the total amount of
vacuum advance in distributor degrees. Double the distributor degrees to get
crankshaft degrees.
Have fun and merry xmas.
John
On Thursday, December 23, 2004 7:11 AM, Michael Marr [SMTP:mmarr@nexant.com]
wrote:
> > wrong one. The
> > number on the advance is 2-6-3. He told me that it means that
> > the advnce moves
> > the timing 2 degrees when the vacuum is 6 millimeters of water and it
> > progresses to a maximum of 3 degrees advance. Pretty neat. I
> > always wondered
> > just what the hell those numbers meant.
>
> I have been pondering this for the last couple of days, and, at the risk of
> being castigated for writing about something of which I have no real
> knowledge, I have to say that this particular explanation of these numbers
> sounds a little fishy to me, for a couple of reasons. First, a vacuum of
> 6mm of water is around 1/4" wg, which isn't very much at all. When you
> consider that 1 atmosphere is about 33 feet of water, then a 1/4" represents
> 6/100% of one atmosphere - the kind of pressure variation you could
> experience just by driving up a small hill! Maybe the units are wrong. I
> could see the 6 representing the number of inches of mercury - a full vacuum
> is about 30 inches of mercury, so I would think 6 inches of mercury is the
> more likely unit, and vacuum is generally measured in inches of mercury,
> anyway.
>
> Secondly, I always thought the distributor maximum advance was much more
> than 3 degrees. Isn't it more in the order of 10 or 20? Or am I
> misunderstanding something here?
>
> I will now sit back and wait to be enlightened...
>
> Merry Christmas, one and all!
>
>
> Michael J. Marr, P.E.
> Naperville, IL
> 1960TR3A
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