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RE: Checking vacuum advance

To: "'Dave Massey '" <105671.471@compuserve.com>, Mark Hooper <mhooper@pixelsystems.com>
Subject: RE: Checking vacuum advance
From: Mark Hooper <mhooper@pixelsystems.com>
Date: Fri, 21 Jun 2002 21:48:50 -0400
Cc: "'Triumphs Mailing List (E-mail) '" <triumphs@autox.team.net>
Sigh... I am being set straight on all sides it seems. Clearly I have a
vacuum retard unit, not an advance. Doh! Clearly time to throw myself in the
lake with my SECAM unit. I will post the pictures of the Sturgeon
tomorrow...

Anyway, vacuum is present, no impact on idle, implies busted vacuum retard
and the reason why my idle is too high.

How do you fix these things?

Mark

-----Original Message-----
From: Dave Massey
To: Mark Hooper
Cc: Triumphs Mailing List (E-mail)
Sent: 21/06/02 8:15 PM
Subject: Checking vacuum advance

Message text written by Mark Hooper
>I have a distributor with only the vacuum advance on my 72 TR6. Last
night
while tweaking the carbs a bit, I pulled the vacuum feed off the
advancer
just to see what effect the unit had on the idle speed. Apparently none
at
all. Is that normal? How should I check this thing? Does sucking on the
pipe
give enough vacuum to see the points mounting plate in the distributor
move?
Is there some way to measure if the advance is working well or poorly,
or
is
it simply working or not?
<

Mark, if the vacuum is from a port on the top side of the carb (as it
should) then you will see no change at idle.  This is because this port
is
ahead of the throttle plate when the throttle is closed.  It is
positioned
in such a way that once the throttle is opened this port will be behind
the
plate and will at this time see vacuum.

You can typically create enough vacuum to see the plate move by sucking
on
the tube and if you do this while the engine is running you should see
the
speed increase.  If it decreases then what you really have is a vacuum
retard (typical if the US cars) and it should be plumbed to a port on
the
bottom of the carb that had vacuum only when the throttle is closed.

Cheers

Dave

P.S. NTSC: 525 lines at 60 Hz scan rate, PAL: 625 lines at 50 Hz scan
rate.
 Secam: a way to photograph fish.

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