OK gang, I have a mystery on my hands. I rooted around many an engine compartment at Homecoming, talked to several people, and still have no answer.

The coolant temperature in our FIA car will not stabilize. It doesn’t overheat; it just doesn’t come to a stable temperature. The car heats up to 180 degrees, thermostat opens, temp falls to 160 degrees, slowly rises to 180 again, t-stat opens, temp falls to 160 degrees, and so on. It just will not steady out around 180 degrees like it should.

The cooling system is identical to Dad’s 427 car: nothing but radiator, water pump, 180 degree stat, inline Moroso filler, 16 pound Stant cap, and a Canton coolant recovery tank over on the passenger footbox. With both the original 302 and now the 383W stroker, Dad’s car runs a rock-steady 180 degrees. With our 351W, we get the ~20 degree fluctuation.

Now, here’s where things get stranger. This exact same 20 degree fluctuation was happening when we bought the car. Only then, it had a 160 degree stat, and the variance was between 140 degrees and 160 degrees. I changed the stat, thinking I’d warm the engine up as well as fix the problem, but the fluctuation remained, just shifting upwards. I’ve also changed the temp gauge and sending unit – identical readings, so I’m not dealing with a gauge ghost. I’ve filled, bled, and otherwise made sure that the air is out of the cooling system. I’ve even moved the temp sensor from one coolant port to another in the intake just to see what happened, but no change!

Thermodynamically speaking, the only real differences between the two cars is that our FIA car has an oil cooler and iron heads, whereas Dad’s car has no cooler and aluminum heads. Still, it looks like the thermostat would even out the temperature right around 180 or 185 degrees.

So, anyone have any ideas? I’m convinced that I'm "too close to the issue" and there’s something minor that I’m overlooking. (I suppose the only thing I haven’t been into is the water pump; but what could be the problem there???)