Ah well better lucky than good.
Problem solved but it was a very unexpected solution.
A little recap. About a year ago my 73 with a factory
rebuilt thermoquad started running crappy. She would
cough off idle and was very flat at top end. Vacuum
readings were low, in the 17 range when a few months
earlier it had been 20.
None of the traditional vacuum leak tests show any
results including Dick B's trick of covering the
primary with cardboard and seeing if the rpm increased
before it died. I set the timing and tune over and
over and there was no significant change.
Last week I replaced a drivers side exhaust manifold
(forearm is STILL sore from banging it on the brake
booster repeatedly). In the process of doing this I
noticed that the plugs were heavily sooted but my
spark indicator showed that all were firing strong.
Checked the firing order again and again.
Based on the lack of vacuum leak test results, i had
about decided it was the carb and, in fact, pulled an
Edelbrock from my son's Mustang to try a different
carb. Of course the linkage was not the same and
before I messed with rigging something up I decided to
change the plugs. No rational reason for this after
all they were 'new'. The old plugs (AC) are about 2
years old but 'new' in that they only have 3-4K miles
on them. It was just a cheap, eliminate a slight
possibility kind of thing. Autozone only had Bosch
and I got the cheap ones since I was just testing.
BANG! What a difference! Vacuum back up to 20. Idle
is smooth, power is strong. She be back! There is a
moral to this story but I'm not quite sure what it is
yet. Reminds of my English Lit classes. Didn't
really enjoy the process and never quite came up with
the same conclusions as the professor...
The only complaint is that in passing gear at WOT she
seems to stay in passing gear a little TOO long. I
say this because the rate of acceleration falls off
and then picks back up when she shifts into high. The
shift point from 2-3 seems to be about 70 at WOT. If
I punch it at 65 she sometimes will drop into second
for just a second and then back to high.
That however is a completly different problem and I
will research it later. For now, I'm going to change
clothes and go for a drive in the rain. The 64 is in
the shop drying off. She has a squeek in the front
end.
In the tlc department, the 73 also had a squeek in the
rear end and I tracked it down to the upper shock bolt
being just a tad loose. Tightened it up and no more
squeek.
I am a MUCh happier camper. Now I just need to think
about what she was telling me and why it took me so
long to fall into the solution. Is there a way to
tell that the plugs are misfiring under load?
Someone asked how to change plugs on a 71. On the 73
(similar) the 1,3,5 4, plugs can be reached from the
top. The #7 plug from below and I had to put a wrench
on the end of my plug socket as there was no room for
the ratchet. #8 also is easier to come out from
below.
Having said that, there is below and then there is
below. Being on a creeper makes for a different arm
angle than standing up with the car on a lift.
One final trick is because some of the areas are so
tight it is difficult to start the plug back in the
hole. You can take a piece of vacuum hose or (my
preference) a piece of 1/8 id flexible water line and
put that over the end of the plug to act as an
extender. For several of the plugs this is the only
way I have found to get them started.
happy happy..
Kerry
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