triumphs
[Top] [All Lists]

RE: Distributor Points Plate Action

To: <triumphs@autox.team.net>
Subject: RE: Distributor Points Plate Action
Date: Mon, 9 Aug 2004 14:26:16 -0700
> I'm now wondering about the vacuum advance.  How freely should the two
> contact breaker base plates move against each other?

A fair amount of drag is normal.  Some expensive cars had bearings between
the plates, but not Triumphs.

>  Mine take some effort  to
> rotate, and I can't imagine the vacuum from the carb being enough
> to move  them.

The force of the vacuum is multiplied by the area of the diaphragm.  Not
much force when it's only a 1/4" (or smaller) hole, but the diaphragm is
much larger.  It's a square law, each doubling of the diameter multiplies
the force by 4.

> By hooking up a tube to the vacuum input, I
> can get the
> plates to move a hair or two (using NAFTA-sized sucking  action).
>  Should it take this much effort?

I assume you're talking about lung power rather than a MityVac or whatever
... yeah it's normal to not be able to move it much by sucking on the hose.
A MityVac is fairly inexpensive, and a worthwhile investment IMO.  Here's a
nice kit on eBay with a buy it now of $50
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2486548090

The factory service manual has specs for actual vacuum advance for different
levels of vacuum, so with a MityVac, you can check the overall advance
mechanism and make sure it's working properly.

Or if you have an air compressor, HF sells an air-powered vacuum pump that
will do instead.  It's worthless for it's stated purpose IMO, but makes a
good vacuum source for testing automotive systems once you add a vacuum
gauge and an adjustable valve on the air inlet.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=3952

I see it's priced at $15 now, but it's frequently on sale for $10.  Add a
canning jar and some tubing, and it's perfect for changing brake or dashpot
fluif.

Randall

Check out the new British Cars Forum:
http://www.team.net/the-local/tiki-view_forum.php?forumId=8




<Prev in Thread] Current Thread [Next in Thread>