Re: [AMC-List] Duraspark distributor woes (258 six)

[Tom Jennings <tomj@xxxxxxx>]

On Thu, 26 Oct 2006, Jim Blair wrote:

> The vacuum advance would be your extra degrees for "total"

Well, yes and no, from what I can tell.


Concerning only wide-open-throttle, first:

I know I'm not racing, though WOT simulates it a bit; zero
vacuum, timing is static+mechanical.  I believe under this
circumstance I should be able to run 36 - 38 degrees total
advance (for the six).

Racing, where a lot of time is spent at WOT, there's often no
vacuum advance unit, economy isn't a concern. 

Back to the actual highway -- at cruise on the flat and level,
vacuum is relatively high, therefore the mixture is rarefied,
which burns somewhat like "lean", more advance -- over the
maximum WOT value -- is recommended for economy, because the
rarefied charge burns slower and needs more ignition lead time.


At least this is what I've figured out by reading (sometimes,
actual books :-)




But assuming you are right, it means the cruising vacuum --
whatever it would be, depending on engine size, cruise speed,
axle and tire, altitude, etc -- should create the right amount
of advance, in my particular case 6 - 8 degrees advance.

I can make a chart of advance vs. in hg with my vacuum gauge,
in the car. I will do that this weekend.

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