Redwood

That's the gusher test? Drain the engine coolant?

1971ChevelleSSV8

I think a good way to flush your block is to run some vinegar in your car and drive it around for a while after it gets to normal operating temp. Removes rust and other deposits. Then drain that and refill with some water and the normal flush stuff and also get to running temp so it can get in the engine. After that open the drain plug but leave a hose in the radiator so all the old water gets out while you're technically still supplying water to the engine to keep it cool. After that. fill with water/antifreeze and Bars Stop Leaks for insurance.

1971ChevelleSSV8

Well a few things, I agree that if those things are new and good, check your fan if it is a clutch fan. Clutch could be going bad, someone mentioned how to test that. Also, did this just happen right after a new pump was installed? If so, maybe you got a reverse flow pump instead of standard, or vice versa (don't know what the RX's normally use). Also, I don't know what the temp redline is on the rotaries, but Dramon says he knows not to go over 200...if he's right. Either way, do you know what temperature thermostat you have, and how do you know it's working? You can test by putting the t-stat in a thing of boiling water with a thermometer, and the temp it opens up at is what temp thermostat you have. If you have a 195, for example, the t-stat will get to 195 degrees before opening and letting water go through, which would then be close to the 200 degree 'redline' and show you're overheating. To fix that just get a 160 or so degree t-stat, opens at a lower temp so the water can move through the cooling system and stay at an overall cooler temp.

1971ChevelleSSV8

Oh yea, one other commonly overlooked thing is the radiator cap. Could be old and need to go to a higher pressure one. I just wanted to throw that out there, but really doesn't sound like that would; be causing the problem, but you never know.