[DeTomaso] vacuum advance on Duraspark II systems
ProvaMo.com
Pantera007 at sbcglobal.net
Fri May 9 18:47:43 EDT 2008
Thanks Bill, your answer was clearer than mine.
And on my car I have a port off one carb metering block.
Seems to work - grin.
Chuck
-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of SOBill at aol.com
Sent: Friday, May 09, 2008 2:50 PM
To: lee_farrell at sbcglobal.net
Cc: detomaso at realbig.com
Subject: Re: [DeTomaso] vacuum advance on Duraspark II systems
Lee,
Holley carbs typically have two vacuum ports: one above the throttle
plates;
one below the throttle plates ( called "ported" vacuum).
The one below the throttle plates has full manifold vacuum. Full manifold
vacuum is max when the throttles are closed and near zero at wide open
throttle. If you connect this port to the distributor, you will have max
vacuum
advance at idle and whenever the throttle plates are nearly closed ..... as
in
cruising.
The one above the throttle plates has zero vacuum at idle, the vacuum
increases as the throttle plates begin to open, and then falls off again at
wider
throttle openings. If you connect this port to the distributor, you will
have
zero vacuum advance at idle (which can make for a smoother idle), normal
vacuum advance at part throttle, and zero vacuum advance at wide open
throttle.
Modern cars, when they still had distributors used ported vacuum.
Be aware that this is a semi-religious subject.
SOBill Taylor
sobill at aol.com
**************Wondering what's for Dinner Tonight? Get new twists on family
favorites at AOL Food.
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