1961 Corvette with 1963 327/ 4bbl/ manual trans. Owned 27 years, the last few years little use and gradual temp increases. Several years ago I put in a 180 thermostat (because of temps in the 220s), took it out, maybe I put it back??. I can't remember.
Except for the temp gauge, you wouldn't know there was a problem, although I started driving the car only when the ambient temps were in the 50-60's and terminated any prolonged excursions at 220 or above: doesn't puke coolant, correct timing and dwell.

Here is my data after using the infrared thermometer: I took the bottom hose temp from the rubber itself (is this accurate enough)

1. My Corvette temperature gauge correlates with the IR thermometer fairly close
2. Car at idle for 15 mins (outside temp 70 degrees) bottom hose 120/therm housing 150
3. After 15 mins highway: bottom hose 145/ therm housing 220
4. After a shower on the radiator with garden hose for 5 mins, bottom 135/therm housing 180
5. Fan clutch cold with quick flick of the wrist: blade moves from 10 o'clock to 2 position, actually does the same thing and feels the same when at 220 degrees.

If the radiator is partially clogged should I have "relatively cool temps" at the bottom hose as above with a radiator water spray?

With above data even if the thermostat was out should I just order the replacement radiator or make sure I have a 180 thermostat in place first and repeat?

Should I replace the fan clutch since resistance feels the same when cool and hot?

I must confess, I haven't been as attentive as I should have been to the coolant changes over the years (last one 6 years ago).

Could the water pump be part of the issue?

Essentially the cooling system contains the same components over the last 27 years (except the thermostat) which it may or may not have; the radiator is Harrison aluminum, heater hose etc. set up correctly, expansion tank cap unfortunately is generic 13lb.

Thanks
Tom

 

Tom,
Before getting to carried away, I would remove the cap from the expansion tank and observe the coolant level when the car is cold. Start the car and bring to operating temp observing the flow in the supply tank. If there appears to be a constant flow you probably never put back the thermostat way back when. If that is the case, do a complete and thorough flush of the cooling system, install a 180 degree thermostat and a 50/50 mix of Zerez G-05 and distilled water and start your observations over again. Hope this helps.

 

The default answer is your radiator is 54 years old well past its useful life.
Replace with an aluminum stacked plate one from DeWitts. Flush out the cooling system including removal of the block plugs. Use a HOAT type anti freeze and distilled water for coolant. Not likely a waterpump problem.

 

I totally agree.... I have a 327 in my 59 and for many years I had a overheating problem to the point it was undriveable. I tried everything... but it wasn't until I put in a Dewitts a few years ago that the problem was solved.... now runs no hotter than 180 (has no thermostat) even on 90 degree days.. if I pick up heat while idling, it will quickly cool down once underway....

 

Thanks for the replies. I'll get the new radiator and flush the system.

Tom