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Re: vacuum advance (Why have it?)

To: Pual Burr <tigerpb@ids.net>, Triumph List <triumphs@autox.team.net> charset=ISO-8859-1
Subject: Re: vacuum advance (Why have it?)
From: Tony Rhodes <ARhodes@compuserve.com>
Date: Thu, 5 Oct 2000 17:58:22 -0400
Message text written by INTERNET:owner-triumphs-digest@autox.team.net
>Date: Wed, 4 Oct 2000 21:53:16 -0400
>From: "Paul J. Burr" <tigerpb@ids.net>
>Subject: Re: vacuum advance (Why have it?)
>OK, here's one for the collective.
>I've got a '74 TR6 with the retard only dizzy. The engine has Weber
>downdrafts and the vacum line for the distributor piped directly to the carb
>vacum port. My question is, was there some sort of bleed off valve that
>enabled the retard at idle only?
>Should I remove the vacum line and plug the port just to see what happens?
>Paul Burr

Paul, I had the same issue on my TR7.  I thought at first the dizzy had a
vacuum ADVANCE, and really wanted to attach a vacuum line from my weber 32/36 
DGV's
to the dizzy.  So, I found a vacuum tap on the carbs and then proceeded to find 
out
what vacuum it delivered at what throttle position.  I found that with the 
throttles
closed, the vacuum tap had zero vacuum.  At partial throttle it went up to 15+
inches, then dropped off as the throttles opened more.  Just what I wanted!  

Well, I then put my mityvac on my dizzy and pulled some vacuum on the "advance".
I expected the idle rpms to increase somewhat.  The rpms DROPPED.  I then found
that the TR7 dizzy is a vacuum RETARD system.  Maybe at idle you want that, but 
certainly
not any other time!  With the vacuum tap on the DGV carb, you sould NOT activate
the vacuum retard.

Just my opinion based on my testing.

-Tony
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