I just had the heads on my 70 GTO 400 rebuilt after about 12 yrs and 30k miles. While it did run hot (above 225) in the summer, it never overheated. The machine shop said there was a lot of scale and junk in the head coolant passages, and since it was running hot, to be sure I had the block flushed too. I also put in a new "desert cooler" 4 core radiator and kept the 195 degree thermostat. I haven't run it that much since, but it does seem better, however the weather is much cooler now too. If I flush the system myself, with the Prestone type kit where you install a water hose hookup into the coolant hose to the heater, will that do the job or do I run a risk of flushing scale from the block into my new radiator? I already tried some local shops that have a B&G flush system that keeps the junk out of the radiator while flushing the entire system but they said it wouldn't hook up to my car--too old. Thanks

I just had the heads on my 70 GTO 400 rebuilt after about 12 yrs and 30k miles. While it did run hot (above 225) in the summer, it never overheated. The machine shop said there was a lot of scale and junk in the head coolant passages, and since it was running hot, to be sure I had the block flushed too. I also put in a new "desert cooler" 4 core radiator and kept the 195 degree thermostat. I haven't run it that much since, but it does seem better, however the weather is much cooler now too. If I flush the system myself, with the Prestone type kit where you install a water hose hookup into the coolant hose to the heater, will that do the job or do I run a risk of flushing scale from the block into my new radiator? I already tried some local shops that have a B&G flush system that keeps the junk out of the radiator while flushing the entire system but they said it wouldn't hook up to my car--too old. Thanks

I personally wouldn't run any flush stuff through mine. Could kill the water pump. Flush it with clean water and then let nature take its course. Read this thread.
http://forums.performanceyears.com/g...11&m=739108469

Great info, and this is a great forum.
Appreciate the comments and pointing me in the right direction.