Bill---From what I've seen, early Triumphs had the vacuum advance, which
operated from a port on one of the (SU) carburetors.
In 1969 they came equipped with both a vacuum advance and a vacuum
retard. (and ZS carbs) This combo pulled against the points plate from
different directions, according to engine load and throttle position
(linkage operating a trumpet valve)
In 1970 the TR6 had only vacuum retard and operated from a port on the
ZS carb, and only at idle speed, when the throttle plate was closed.
There was no "temperature compensator" between this source of vacuum and
the distributor.
However, I think all of these cars with the vacuum retard only, should
have their timing set one particular way...that being to adjust the
distributor position to where the timing at idle speeds (below 900 rpm)
gives an advance of between 10 or 12 deg. BTDC. No magic or secrets
here!
Reconnecting the vacuum retard line to the canister will then retard the
timing approx.14 deg., which brings it back to 4 deg. ATDC at idle.
IF the vacuum to this retard canister is connected to the wrong carb
port, it could advance the timing at idle, when it shouldn't.
All of this has been written many times, so I'll shut up, already.
A timing light is a good investment, if you really want to know what
your mechanic seems reluctant to disclose!
Dick
From: anabil007@comcast.net(Bill & Skip Pugh)
tr6taylor@webtv.net ('Sally or Dick Taylor'), 6pack@autox.team.net
Subject: RE: FW: Ignition Timing anomaly
I have been told (by folks wiser than I) that there are at least three
(3) different distributor advances for the TR6 ... vacuum advance,
vacuum retard, and vacuum advance & retard. It turned out that mine had
an incorrect dizzy for that car, should have been a vacuum advance, but
instead had a vacuum retard. At that point we had to ignore the "
correct " timing marks and "wing-it". After much testing/trying/testing
we finally hit upon an advance that cured the "below 2000 rpm stutter".
I would share that with you but my mechanic refuses to reveal the secret
... all I can say for sure is that 4 deg before TDC was WRONG ... I am
still working on him, and sooner or later the Chinese water drop torture
will get him to confess ... >:-}
--
Bill Pugh
1957 TR3 TS16765L
aka
Casper
1970 TR6 CC59179L
aka
Rosey
Wallace, CA
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