Not sure how this '77 radiator got so messed up. I've had the car for 10 years and it has always had distilled water and coolant in it. No idea what the previous owner did to it though.
A few years back, I had to replace the T on the front of the head due to massive corrosion. That was probably the first clue that something was not right inside.
When I got the car, it always ran with the temp needle right in the middle (maybe just a hair past). I found this mod the t-stat. The whole is big...3/8" or so. I have this t-stat installed right now and the engine is running a little cool. I have a new t-stat from Vick (which isn't super easy to install) that I put in before. When it didn't help, I removed it, but will likely put it back in.
Sonny