[TR] tuning

[Randall]

> Randall,  Perhaps you know of one that is better, but here is an
> article on tuning the MG which has some application to the TRactor
> Motor:
> http://www.mgcars.org.uk/mgtd/mgtd_tuning_your_mg_july_52.htm
> Changes that I know for the TR3 include

I think every number I saw in that article is wrong for a TR.  In addition,
there are several things I do not agree with, including using a wire brush
to clean spark plugs.  The wires will leave microscopic particles of steel
embedded in the ceramic, which makes the plug more likely to misfire.  I
generally don't clean plugs at all, as with modern unleaded gasoline they
shouldn't foul nearly as rapidly as they did back in the 50's.  Unless of
course there is something else wrong, and in that case I generally just
replace them.  But if you do want to clean them, I suggest an abrasive blast
cleaner rather than a wire brush.

For points, if you want to clean them, I suggest a "contact burnishing
tool".  Although less common today, they are still a standard repair tool
(normally used to clean relay contacts) and they can be used with the points
still assembled in the distributor.  If they are really worn enough to
require dressing (and bending) back to flat, just replace them!

Haven't tried it myself, but I'm guessing that his procedure for setting
timing will wind up with it too far advanced on a TRactor motor (taking into
account the CW vs CCW differences).  

The "drill trick" seems like too much work to me.  If you just install the
piston in the dome and spin the piston, you can easily see whether the
needle wobbles or not.  If so, the needle is bent.  (I should also admit
that my cheap drill press does not run perfectly true and so there will
likely be some wobble shown there even if the needle is perfectly straight.)

>    After this step, it seems to say, drop the piston and needle into
> it's housing, and it shouldd slide to it's base or bridge w/o any
> hindrance and make the familiar 'clank sound'.  If this is not the
> case, loose the lower brass bolt  till it does.

The nut he wants you to loosen is the large steel nut, located above the
brass nut & spring.  This is the nut that clamps the jet assembly into the
carburetor housing.  With it loosened a bit, move the jet assembly around (I
usually just tap on it with a wrench or something) and then _re-tighten the
nut_.  
It's a trial-and-error process, as the jet always seems to move slightly
when I tighten the nut.  I like to do this adjustment with the brass mixture
nut set full lean (all the way up), as it then assures that there is some
clearance between the jet and needle after the jet is returned to its normal
position.

FWIW, I recently discovered that there was enough clearance on my carbs in
the fit between the dome & main body to affect the needle centering.  By
loosening the 3 screws for the dome and turning the dome, I was able to stop
the needle rubbing.

Also FWIW, I normally do not disturb the dome, needle or jet as part of a
routine tune-up.  As long as the piston moves as it should (no rubbing or
binding, lands with a distinct click), then it "ain't broke" (so don't fix
it).

Once you are done with all this, and have the ignition timing and valve lash
set to specs, you'll also need to readjust the mixture.  12 or 13 flats down
is only an initial starting point, the actual mixture needs to be set with
the engine running.

Overall, while the MG pictures are interesting; I think the Triumph owner's
manual ("Practical Hints for the Maintenance of the Triumph T.R.3") is a
much better reference.  If you don't have one, I strongly suggest you get
one.  Reprints of the 6th edition (suitable for post-60K cars) are available
from the usual suspects, or you can download a copy from 
http://tinyurl.com/3ee76gj

-- Randall