Hi Bob and List,
I'm glad to hear of your success with the electronic ignition on your
TD, and I enjoy reading the activities of the list even though most of it
does not require my direct response, but I had to put in my 2 cents worth
(with a smile) regarding points! This is with the understanding that I am
talking about road cars, not race cars or those seeking extra performance.
There is a certain trade-off of switching to electronic ignition and
abandoning our dear old points, and I hope to stimulate some discussion on
the list with my thoughts here. After working on points ignition cars and
motorcycles for some 35 years, I feel that points have gotten a bad rap in
today's electronic world, and in general are a very reliable way to
stimulate a spark. I might add that so far, with all the British cars and
bikes that I have owned, I have yet to install an electronic unit to any of
my own vehicles, and I do some mileage. So, I'm biased! Maybe someone will
remind me that I wrote this when I convert and wax in adoration of an
electronic unit!
The problems that "standard" ignition systems experience, especially on
these old cars, fall into three categories. First, mechanical problems in
the distributor: worn bushings, sticky advance weights, weak or missing
springs, and points plates.
**Worn bushings cause jumping around of the timing mark while setting timing
with a strobe (and by inference of course, that the spark itself is not
getting there "on time"). There is play in the distributor shaft, so how do
you set the points... with the shaft pushed, or pulled, or maybe halfway in
the center? Setting of the points by dwell angle rather than just gapping
helps in this situation but does not fix the problem.
**Sticky advance weights can usually be fixed with dismantling, lubrication,
and reassembly.
**Weak or missing springs cause the engine to hit full advance too soon,
causing excess pinging and scratching of the head. The timing will appear to
be at specs at idle, but advances too quickly.
**Points plates may have wobbly pivot pins or may slip due to bodged hold
down screws from a prehistoric mechanic (we all started there!)
Fix the mechanical stuff no matter what kind of ignition you are using,
and a long and useful life of the ignition system will result. When the
distributor is in good shape, and the points are gapped properly, timing is
not difficult. I have always done a "seat of the pants timing" after setting
to specs anyway, and could usually advance timing a bit more than specs. If
it doesn't ping, advance to where it does, then back it off a tad. On later
BMC cars like Bs, Spridgets, Healeys, or Triumphs the "micrometer"
adjustment on the outside of the distributor makes this a snap. If the car
does not spin easily by the starter motor after advancing the timing, it is
too far advanced, but should ping pretty badly too.
Secondly, the points themselves, which are intricately linked to the
third, the condensor. As a mechanical device the points just need a little
lubrication on the pin and the cam block and they last a long time. As an
electrical device the surfaces of the points need to be relatively clean,
flat, and parallel. I say relatively because they will tolerate wide ranging
conditions of dirtiness, pits/pips, and off angle operation, before they
fail. The car may not run the best in these ugly conditions, but it will
run. They also will operate at lower than normal voltage (in the event of
generator or battery failure) allowing someone to limp home even when the
lights won't work. With electronic, when voltage falls below a critical
threshold, the car quits - this to me is the main drawback of electronic
ignition. Have you seen charging systems fail?
The pits on points are indicative of the match of the condensor to the
system. If points get pits on their surfaces it means that the condensor
(also called a capacitor) is absorbing either too much or not enough
electrical current. Not a big deal but it shortens the life of the points
and makes them hard to gap. In this case, change the condensor when you
change your points! If there are no pits, I have left condensors in place
for YEARS, even on customer's cars, and they have been entirely reliable. I
can think of only two cases in my lifetime of condensors actually failing.
Yes, there were probably more, but I can't remember them now! On a twin
cylinder bike, it just runs on one cylinder because there are two
condensors. In a car, of course, its a different story.
A set of points should last 12,000 miles or so, which for a typical
hobbyist (with a running car) could easily be 12 years of reliable running.
If not running, maybe 50 years!
I'm sure this will start more email than we care to read, and may beat a
dead horse, but in the microwave "I haven't got all minute!" mentality that
many car owners have, points, condensors, dual carbs, and other
eccentricities about our old cars are vanishing along with the people who
understand them.
I'm thankful to be able to offer my opinion (that's all it is) and look
forward to hearing the discussion that follows.
Best regards to all, Pete Thiel
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