There has been frequent discussion regarding 289s overheating, and my 1965 289 is doing the same thing. After only about five miles of highway driving the temp goes to 220. The top of the engine has been completely rebuilt, overflow tank added, 6 blade fan, 4 row radiator. We've been running pure water through it and took out the thermostat, but still boils after only a few miles. Could the block be cracked? (please say this isn't the problem) I'm almost on the verge of looking for a new engine, but as a last result.

 

Drain the water. Install a thermostat. Make sure the vanes on the WP aren't corroded and the bearings aren't shot. Refill with coolant/water mixture. Check the pressure on your cap.

Pure water does NOT cool as well as coolant/water mixture and will destroy your engine over time without the lubrication and rust inhibitors in coolant. Removing the thermostat by itself is enough to overheat an engine. The coolant needs some time for heat transfer.

 

I usually don't run pure water and without the thermostat, just tried it recently because the coolant keeps boiling out and the water is cheaper than the antifreeze. It was boiling over with the thermostat, but I'll put it back in and see what it does. Thanks.

 

What is the history on this engine? Do you know when the water pump, thermostat and cap were replaced? Have you flushed the engine? One last thing, have you ever replaced the lower rad hose?

 

Bought the car with this engine in the early 1980s, restored the car, didn't have to do much to the engine. Drove it for a several years, ran fine, not hot, then circumstances forced me to store it for almost 15 years. Been restoring the body again in the last few years, and now the engine is giving me fits. I've (actually my father and a few mechanics) replaced and done everything you've mentioned, bottom hose is new with a spring.

 

Take the cap off and start the engine. Let it heat up to operating temp and see if water is running over the top of the fins as like a fast river would do. If you don't have water running over the top of the fins, it could be the water pump. Make sure the water pump is the correct one for that engine. Some go counter-clockwise, and some go clockwise.

 

Was the thermostat in right? It could be a bad water pump.

 

After sitting that long, it's very possible some rust scale has dislodged and is blocking some coolant passages. As Soaring stated, a good back flush is probably in order.