[FC] Why Vacuum Advance?

[Merv and or Loretta]

I also understand that the first 100 or 200 rpm are prettty much from
advance only before the carb gets into the act....?
Merv Krull
Salmon Arm, BC

----- Original Message ----- 
From: <VairMech@aol.com>
To: <corvanatics@corvair.org>
Sent: Thursday, April 08, 2004 4:39 AM
Subject: Re: [FC] Why Vacuum Advance?


> In a message dated 4/8/2004 2:16:56 AM Eastern Standard Time,
> galaxyflyer1@yahoo.com writes:
> But what is the purpose for getting top advance when accelerating only,
> therefore getting a retard when de-accelerating or while the engine is
just idling.
> Why not remove the vacuum line (plug it) and set the timing for peak
advance
> before ping (road test) and therefore have optimum advance all the time?
> >>>>>>>>>>>>>>>
>     You got it all wrong in what you are thinking above.
>     The vacuum advance is a ported vacuum source. After about 3/4 throttle
it
> no longer works and goes to it's retarded position. But, you don't want
any
> advance during acceleration or at idle.
>     So the vacuum advance will advance at part throttle openings and as
you
> open the throttle the advance will retard so you don't get spark knock and
when
> you hold a steady throttle it will advance again. This process goes on all
> while you are driving and with every move of the throttle. As you
decelerate,
> foot off the throttle, the vacuum advance should go to the retard position
> because the port should be covered and this helps prevent backfiring in
the muffler.
>     What the vacuum advance does is give you gas mileage, plain and
simple.
> The distributor can be made to work very well without a vacuum advance but
I'll
> bet your mileage would be cut in half.
>     Now if you want to get into the mechanical advance and combine what
the
> two do together, well it could take several pages to adequately explain.
>     Ken Hand
> _______________________________________________
> Corvanatics mailing list
> Corvanatics@corvair.org
> http://www.vv.corvair.org/mailman/listinfo/corvanatics
> This list sponsored by the Corvair Society of America,
http://www.corvair.org/