Well, the advance has to exist (either in mechanical or vacuum or some
combination of both as the early 6 has) because even as the engine goes
faster the explosion from the gas still occurs at basically the same rate.
Therefore the spark needs to occur earlier in the stroke at higher speeds
for the main force of the explosion to occur at the "right" time.
There is debate over the reason for the retard, some here on the list think
it was for emissions, others think it gives a smoother idle. Me? I am exempt
from emissions testing and have my retard disconnected and think I have a
smoother idle without it. My timing is set 10 BTDC.
Nonetheless there is never a time when both function. Look at the diagram
of advance and retard in the catalogs for the 69 6 (BTW Moss and VB have the
dizzy connections reversed, TRF has it right), but notice that there is a
switch in the line operated by the accelerator shaft. The retard only
functions at "foot off the gas" idle. Moreover, retard is connected to
manifold vacuum, which declines as engine speed increases, as opposed to the
advance line which connects to the carburetor and increases vacuum as speed
increases.
Jim Altman jaltman@altlaw.com Illigitimi non Carborundum
http://www.altlaw.com/metro/jaltman.html 69-TR6#CC28754L W4UCK
-----Original Message-----
From: owner-triumphs@autox.team.net
[mailto:owner-triumphs@autox.team.net]On Behalf Of Janssen, Lee K
Sent: Thursday, October 08, 1998 8:11 AM
To: 'triumphs'
Subject: distributor advance/retard
Could someone explain why the early model TR6s had both a vacuum advance AND
retard??
Thanks for the info.
Lee Janssen
Denver CO
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