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re:vacuum sources and theory

To: "INTERNET:jimmuller@pop.mail.rcn.net" <jimmuller@pop.mail.rcn.net>, Triumph List <triumphs@autox.team.net>
Subject: re:vacuum sources and theory
From: Anthony Rhodes <ARhodes@compuserve.com>
Date: Tue, 26 Jun 2001 15:39:06 -0400
Thanks.  That makes sense. 

Actually, I do not have a TR6.  I have a TR4A which has vacuum advance, and I 
like it that way.

BUT  I have a TR7 with vacuum retard.  Actually, iy does not have it active at 
this moment.  I have
weber 32/36 DGV carbs on it and the retard disabled.  I hate its piss poor 
power.  

So....  I have obtained some euro-spec SU carbs  and linkage for the car.  It 
appears that the euro-spec
distributor uses vacuum advance.  I have conflicting reports on this.

The vacuum tap in the carb is close to the edge of the throttle valve.  Pretty 
much under the edge when it is closed.
It LOOKS like it would have little vacuum when closed, and then the hole is 
uncovered with cracking the
throttle open.  

This would appear to be a vacuum advance, right?

I also suppose that if the distributor is designed with vacuum retard, then it 
essentially uses mechanical advance 
only.  And further, as you say, that you need less advance at 
wide-open-throttle, then there is a little loss of 
efficiency at part throttle with this design.  Therefore I think I should look 
for an advance-type distributor....

-Tony

Message text written by INTERNET:jimmuller@pop.mail.rcn.net
>The retard acted at 
idle only, and went away quickly under power.  Its purpose was strictly 
emissions control.  The advance would be fully on at idle, and gradually go 
away as the throttle was opened up more and more.  Its main purpose would be 
increased fuel mileage, and possibly some response immediacy at part-
throttle.<

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