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RE: mechanical advance

To: "triumphs" <triumphs@autox.team.net>,
Subject: RE: mechanical advance
From: "Randall" <tr3driver@comcast.net>
Date: Thu, 16 Jun 2005 08:07:44 -0700
> First of all: The factory manuals or the group with their accumulated
> experience and all working together would be the best sources as to what plate
> (or maximum advance) should be used.

Jim sounds like a nice guy, and I'm sure he knows all about distributors.  But
he doesn't know Triumph manuals !

> Secondly: Keep in mind that distributor advance is half of the engine advance.
> In other words, if the max distributor advance is 10 degrees, that would
> translate into 20 degrees of engine advance.

Good point, but some manual entries are given in crankshaft degrees instead of
distributor degrees.  And, I know of at least one Triumph manual (Stag, not
TR3A) that specifies crankshaft degrees but the numbers given are in distributor
degrees !

> Fourthly: The next question is - - If there is a vacuum advance, at a cruise
> configuration of 2750 engine rpm, how much vacuum advance is obtained.

As a general rule, there will be more than enough vacuum at mid-range cruise to
obtain the maximum vacuum advance.  This is the third number (in distributor
degrees) in the three number sequence (eg 7-14-10).

> If the
> centrifugal advance cranks in too much and then the vacuum advance adds some
> more, one can get too much advance.

Yes indeed, which can damage the engine.

Randall






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