Hi Denny,

Do you believe it is all wrong.?

It was my belief that a richer mixture under load would take longer to burn
than a leaner mixture, however, the PDF you linked to indicates otherwise.
And wiki says "...to advance the timing at low to mid engine load ..."

Googling seems to indicate that some earlier systems used manifold pressure
while later systems used ported vacuum (which I was referring to).  And
others used both.

Manifold pressure systems having full vacuum at idle and ported vacuum
systems have little or no vacuum at idle.

More research for me is in order.

Justin


>
>
> I remember I was puzzled for some time when I tried to understand vacuum
> advance as i knew that the vaccum falls away to nothing at cruise and at
> high acceleration.  At cruise or acceleration I considered that there
would
> still be a requirement for advanced timing but the fact that there was
> little vacuum at cruise or acceleration seemed to be a contradiction.
>
> It wasn't until I noticed that the vacuum pickup line was taken from the
> base of the carby body where at high cruise or high acceleration there is
> an increased volume of air passing thru.  High volume thru the venturi
> equals high vacuum and vacuum advance to assist the mechanical advance.
>
>
Sorry for the hijack, but this is _wrong_.
A quick google gives this reference with a much better explanation than I'm
willing to type up
http://www.camaros.org/pdf/timing101.pdf on about the fourth page.

-Denny
(crap, am I now "that guy arguing on the internet"?)
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