Thanks to all those who replied.
"Overheating" is a relative term, different for different vehicles. When
you breathe on a given motor and make more horsepower, you automatically
make more heat. Your cooling system may or may not be up for the job. I
was looking for some idea of what is an acceptable operating temperature
for my "breathed-on" Tiger. Your responses indicate that 220 degF. is a
reasonable temperature for a motor in my motor's state of tune.
Well, I am writing to report a breakthrough in my "overheating" problem.
Unbelievable actually. It turns out that the P.O. fitted my motor with a
Mustang water pump. As most of you likely know, this water pump has a
heater outlet and inlet nipple. On my car, the heater was fed from the
water pump, and the return line from the heater core is plumbed into the
intake manifold, as originally configured. But the P.O. connected the
water pump return nipple to a nipple on the thermostat housing. This had
the effect of circulating a fairly large quantity (about 20%) of the
coolant continuously back into the intake manifold, without travelling
through the radiator. Presto: very hot motor.
We blocked off these two nipples so that all of the coolant coming out
of the thermostat went to the radiator. We also removed the thermostat.
In 72 degF. weather, we could not get the temperature gauge to rise over
170 degF!
Life is good and "cool" again. The car is performing like gangbusters,
and we are going to re-install the 180 thermostat to try and get the
coolant back up to 190 or so.
I hope this is helpful to someone else!
Cheers and thanks again for all your help and ideas,
Dave Munroe
Nova Scotia Tiger
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