Originally Posted by Bluepen
I've got a '78 350 SBC in my '46 Chevy Panel and now for some reason it's running hot. It was holding at 195 on short to medium runs around town but now it's going to 205/210, don't want to run it any higher. I had a 180 stat in it and dropped it to a 160,it helped a little but just took longer to start to overheat. I'm also using the stock copper and brass rad. I know I could do better with that but funds in the way. The fan is a 17" electric with 2700cfm. Now it runs real rich and need to change the jets in the carb, 625 cfm Road Demon. Could the rich condition be the cause of the over heating?
Overheating while the vehicle is in motion is a classic symptom of insufficient coolant flow thru the radiator or one that is too small for the job at hand. Cleaning the radiator at a competent shop that can "rod" the core is the inexpensive solution. The copper/brass and lead based solder that hold it together react in the presence of water, whether that water is diluted with anti freeze or not. The reaction also includes the cast iron of the engine and if you have aluminum heads they get into it big time.
Anyway, the corrosion acts in two ways, one it removes the softer materials which will eventually result in a leak. Two, it deposits materials which cause the tubes to become plugged, thus reducing flow. Rodding the core takes these deposits out. It doesn't solve the decay problem, however, it could buy you some time.
Barring that being a successful fix a new radiator will be in order to solve the problem.