Bob---Well you certainly wrote plenty of information about your latest
concern, but I, for one, would like to include a lot of questions to be
replied to at your convenience. The information needed will include
some of the possible causes.
1. Did the overheating start when the compression was raised, OR after
the cam was changed? Did you install a stock grind cam?
2. Is the thermostatic vacuum control tubing still connected to the
distributor retard? Does it work?
3. What does the temp "creep" to? (It's normal for most TR's to move up
a half notch on the gauge when idling for a while. (But not in a
"minute, or 60 degree outside temperatures.")
4. What's the pressure rating of the radiator cap? (7 lb. is OK, but
13lb. allows a higher temp before boiling starts.)
5. Is your radiator shroud in place?
6. Has the radiator itself been tested for flow rate lately?
7. I will assume it starts to overheat even with the "air" off.
8. Can you go back to a place in time when this was first noticed? Often
it happens when a certain part was changed, or an adjustment made that
influences the cooling of the engine.
9. Does the fuel line come in contact with anything hot? (Loss of rpm's
as temp rises could mean possible fuel boiling.)
10. Engine run-on is common if the anti-run on feature isn't connected,
especially if the idle is set too high.
11. Replacing your thermostat to one with a cooler rating (165 degree)
will buy a longer period before the "creep" goes past the half-way point
of the gauge, but won't likely stop the creep.
I don't think the answer lies in the points, valve adjustments, carb
tuning, or the like.
I know there are many owners that feel they needed a supplemental way of
keeping their engines cool, either by larger radiators, or extra fans.
I've never had the need, but maybe it's just dumb luck. Raising the
compression ratio may have been at least part of your cause, but I can't
believe this alone would be the only thing going on here. Modern engines
typically run much warmer than they did 25 years ago, with no ill
effects. I do know there's a confidence window when it comes to water
temperature, and those of us that watch our gauges don't want it on the
outside. Please let us know what you find after reviewing the above.
Dick Taylor
'73
L.A., Ca.
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