Hi Dave,
I have the same issue. The warmer the temperature outside, the warmer the car will run.
I like to drive mine. I recently drove from VA to KY to surprise my dad and go to some car shows with him. The car did well, staying around 190-195 running 60-70 mph. Reached about 200-210 going up some of the longer mountains.
Although I do not really feel 200-210 is too hot, I want mine to run closer to the thermostat (180). In cooler, less humid weather, it runs about 185 at just about any speed. In hot, humid weather it runs 200-210 down the highway.
Is it possible that the original radiators are just not efficient enough for prolonged driving at higher rpm?
What I've done:
1. Switched from a 3 to 5 blade pump.
2. Had radiator pressure tested (ok).
3. Installed new 180 t-stat, tried 2 different ones.
4. Installed new 16 lbs cap, tried 2 different ones.
5. Replaced all core plugs/freeze plugs/expansion plugs or whatever you want to call them. Therefore, I was able to see into water passages, where one would not normally be able to see into. I did not encounter anything that would suggest restricted passages, but again, I could only see small sections of the water passages.
6. Timing. Timed it both with a gun and by ear. Even if the ring has slipped on the balancer, I've had it so advanced and so retarded, I think I've eliminated a timing issue.
7. Converted to electronic ignition and vacuum advance works.
8. Installed new plugs and wires.
9. Checked lower hose for collapse at high rpm. No collapse detected.
10 Bypassed heater core (run with and with it bypassed).
11. All hoses are in good condition.
12. I use the wiper fluid bottle for an overflow container. Air bubbles are never present.
Side note: I am running a flex fan with no shroud. However, those things should not matter at highway speed. 3 speed without air, has the larger pulley.
Nothing I've done has made a change in either direction with regard to operating temperature at highway speed. The only things that have affected operating temperature are outside temperature and load on engine.
So, what is left?
Running too lean?
Head gasket?
Insufficient flow through water passages?
Overbore?
Insufficient radiator?
Can anyone recommend an aluminum radiator? This will the next thing I replace. I'll let you know how it works out. If that doesn't cure it, I'm just going to disconnect the gauge.
The photo is of my car with my dad's '49 Ford in Harrodsburg, KY. There were 3 Buicks there. I think mine travelled the furthest though.
-Joe
