Subject: [Mg-t] The TD Is Revived...

From: Scott Fisher <[email-masked]>
Date: Mon, 29 Apr 2013 10:20:11 -0700 (PDT)

So after nursing my new-to-me '51 TD home last Monday (swapping in a spark
plug at the roadside, to replace the one on which the ceramic had snapped in
two), I set about making a few discreet inquiries, as they say, into what was
up with it.

The dashpots were not quite dry, but certainly very low. Adding a
little light oil (actually, ATF, which I understand to be the active
ingredient in Marvel Mystery Oil) brought the level up above the brass dampers
on the rods. I still suspected much of the trouble to be in the ignition, so I
pulled the distributor cap.

The cap had no cracking or tracing, but the
carbon brush didn't retract very far when I tested its spring, suggesting it
was quite worn. The rotor had the usual discoloration indicating it was
well-used, but didn't seem abnormally so. The points gap seemed appropriate at
0.012" but my feeler gauges (which have spent many happy hours under the
rocker arms of my Midget and MGBs) are a little large to fit into the TD's
dizzy.

I was a bit more concerned with the advance mechanism. The rotor
WOULD turn when twisted, but there seemed to be some slop before the weights
and springs engaged. (I've had a distributor wear so much that the pivot holes
in the advance weights were oval, making for scattered timing at full
advance.) I simply added some more light oil down the central shaft and
returned the cap.

The car ran significantly better after this, but still had
some backfiring on acceleration about 3500 RPM. So when I went to the auto
parts store to buy rags, a soft brush, and some other bits for the cleaning, I
also ordered four spark plugs of the appropriate size (Champion L 10,
available at the warehouse, shipped to my local shop the next day). I also
bought a feeler gauge with smaller blades.

On installing the new plugs,
after gapping them to 0.022" as per the manual, I noticed that the #1 plug --
the one which had broken at the roadside, and which I replaced with an old
spare from the box the seller included -- was broken AGAIN, this time in my
plug socket. VERY odd. I think this might be due to the condition of the plug
wires, which are so old and stiff that they barely bend out of the way to get
to the plugs. Could the vibration be transferred into the #1 plug (it being
the longest wire) and weakening the porcelain? 

When I pulled the #4 plug
lead, the wire separated from the clip that holds it to the plug. Damn. I
shoved it back in as best I could and held it in place with some duct tape --
only because I had the car's first official outing the next morning. I had
already ordered the full tune-up gear from Moss, including new plug wires with
the correct screw-on ends, new cap, new rotor, new plate in the distributor
with points and soldered-in condensor, and just for fun, a new Lucas Sport
coil. (Next year: bumblebee plug wires!)

The car started as it always has,
even with only three plugs: a gentle tug on the starter switch and the car
roared to life. But even backing out of the driveway I could tell there was
more throttle response. Motoring down the road, the car felt like an M.G.
again, brisk acceleration and that wonderful straight-cut gear whine in first!
The car pulled strongly past the 5000 mark on the chronometric tach, no
backfiring apart from an incredible snap and burble from the well-worn
exhaust. (It appears to have a single cherry-bomb glass pack in the straight
tube.)

More later, including the car's first public outing and a bit of
"interior design" work...

--Scott Fisher
  Tualatin, Oregon
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From: Richard Lindsay <[email-masked]>
Date: Mon, 29 Apr 2013 18:17:08 -0500

Scott, its time to check your car's compression.  Warm it up then pull
all plugs.  Remove the distributor cap or just remove the rotor.  Open
the throttle 100% and block it open.  Spin the engine on the starter
for about 4-5 revolutions with a compression gauge held into each plug
hole in turn, and record the pressures.  Gauge available at Harbor
Freight quite inexpensively.  After making the 'dry' measurements, add
about 1 teaspoon of motor oil into each cylinder, through the plug
holes, and make the 'wet' measurements, again recording the pressures.
 THEN, post the results here please.

-rick
PS: Remember, "Diagnose BEFORE surgery."

On Mon, Apr 29, 2013 at 12:20 PM, Scott Fisher <[email-masked]> wrote:
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