<VV> custom distributor curve?

kevin nash wrokit at hotmail.com
Thu Feb 21 22:59:12 EST 2013

> Message: 3
> Date: Thu, 21 Feb 2013 15:34:02 -0800
> From: Mark Durham <62vair at gmail.com>
> Subject: Re: <VV> custom distributor curve?
> To: Matt Nall <patiomatt at aol.com>
> Cc: virtualvairs at corvair.org
> Message-ID:
> 	<CAEEoEu7vdjVBsDZqq4UPAq+dPqm7sFGUXVBJEqh4U85AzNCnXw at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> OK Matt, now I'm the dummy. I understand about the three spring kits, but I
> need an explanation of the benefits of removing the vacuum advance.  I
> don't drive my street car enough to worry about gas mileage, but would like
> good steady performance from the engine.
> I also understand the weights and springs swing in and out at different
> rpm's adjusting the advance, hence finding the sweet spot, but how does the
> vacuum advance mess with that? It works off of manifold pressure, but I
> haven't sent any time thinking about the interrelationship between the
> mechanical and vacuum advances in the cars. I would think the vacuum
> advance would continue to advanc the enine beyond the capability of the
> mechanical advance. Am I wrong?
> So, what benefit is there in removing the advance alltogether?
> Mark Durham
There is no performance benefit, nor is there any performance decrease from disabling the vacuum advance in a modified engine, although it is easier to know how the engine is timed
with the v/a disabled. In a performance engine, where the intended use is at, or near w.o.t., the vacuum advance isnt doing anything, because there's not enough vacuum for it to work.
There is, however, a small performance benefit in a modified street car engine to use a vaccum advance can that simply takes less vacuum to actuate. Radical cams, big carburetors,
all cause less vacuum, even at idle, and having a load sensitive component to the timing (instead of being strictly rpm based) using a vacuum advance can that actuate
at lower than normal vacuum levels, makes the car easier to drive on the street, at least for us dummys that cant keep it pinned between stop lights! gggg.
Supposedly, these special low vacuum/advance cans for s.b.c. are available at NAPA for 10.00!! for more information check out: http://www.hotrodders.com/forum/distributor-tuning-theory-part-1-a-59033.html


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