Eddie,
If the cap is bad and it is loosing pressure you would be constantly
adding water. Is the coolant level going down?
Sounds like a combination of a few things to me.
First, you should be running a lower temp thermostat. I run a 165* in
summer. If you are running at 180* or 195* to start with, the water
temp doesn't have far to go to get to an overheat condition. Also,
certain brands of thermostats will react faster than others.
Second, the timing sounds like it is over advanced (or it's over
advancing on acceleration, like going up steep hills). Over advanced
timing is one of the main causes of overheating in the A series 1275,
especially with an engine that has some modifications to it. When you
are climbing a steep grade the timing will be advance during the entire
climb, not like when you accelerate to pass a car on flat highway and
then back off the gas. I'd guess that with the total timing (including
mechanical and vacuum advance) your timing is slightly over-advanced.
Just a few degrees will make a big difference in engine cooling. My
wife's 74 Midget had the same symptoms that you are describing. After
checking the water pump, radiator, and replacing the thermostat, I
retarded the timing just a little at a time until the overheating
stopped. It only took about 3 or 4 degrees.
Take any combination of a few of these and the cause can be a bear to
find.
Put a 165 thermostat in the car and try retarding the timing just a
little at a time and see what happens. Retard just a little and take
it for a ride - watch the temp. then retard again and take another
ride, watching the temp again. If this doesn't help, I'd start looking
at the water pump and the radiator.
I'll be out of town (off list) for the next week, but email and let me
know how things progress.
Good Luck!
Kevin
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