I've got a 69 bonneville with a 1972 400. It runs great around town and on the highway up to about 80. Anymore than 80, after awhile it heats up to the point of the engine pinging/knocking. Slow down and turn on the heat, and it goes away? The temp reads 225+/- 5 degrees. Any ideas? Radiator/block dirty, water pump. The water to antifreeze mix is 50:50.

I've got a 69 bonneville with a 1972 400. It runs great around town and on the highway up to about 80. Anymore than 80, after awhile it heats up to the point of the engine pinging/knocking. Slow down and turn on the heat, and it goes away? The temp reads 225+/- 5 degrees. Any ideas? Radiator/block dirty, water pump. The water to antifreeze mix is 50:50.

it sound like your reaching the point where the cooling system won't handle the heat generated by the engine at those speeds. what kind of rpm is it turning? mike

no idea on rpms it has 2.73 or so gears so not terribly high. Thing is, about a year ago I could cruise at 100 forever without noticing any temp change. Now, 80+ for half an hour and the engine is pinging. Radiator clogged, water passages in the block clogged, cavitating near the waterpump? I"m not positive which it is, I guess the best bet would be to tear it apart and have a look, but I was hoping not to have to do that...

i'd start at the water pump if nothing has been changed since the prior high speed runs. mike

My 66 was fine until a few weeks ago. Went from running 190 all day long to hitting 225+ sitting at the stop lights. Water pump is brand new, new thermostat. I am sitting here as we speak waiting for a new Radiator to be delivered. I noticed that the Rad. had a small hole in it the other day and the channels were pretty clogged. Hopefull this fixes the problem. Not to mention that I am going from a 3 row to a 4 row radiator. Should see a huge differance. Just in time for the hot July/August Florida days. :cool:

Joe,
Let us know what happens with your new 4-row. I just ordered a Summit Aluminum 2 row and am hoping this will cure my "hot-ness". Depending on whose post we read the verdict seems to be up in the air regarding 4-row cast or 2 row aluminum. 4 row seems to work for some applications and 2 row aluminum seem to work for others. I hope we both solve our problem.
Roy

Of course the first one I got was the wrong one. I'll have the right one here in the morning. I look at it this way. Its not a race car, nor have I really done anything performance wise other than a larger carb and larger dual exhaust. The car was running fine with the old 3 row until last week when I noticed the hole. It can only run cooler with the 4 row cast than it did with a clogged dirty 3 row. I'll update tomorrow afternoon when the right one goes in. :rolleyes:

Woke up this morning and the right one was here. I just got done installing it and wow, what a differance. Hasn't come off 190 all morning. Im gonna go get something to eat and see how it does in traffic. Wish me luck.

Keep us posted Joe......good luck.
Roy

Running fine now. 4 rows are the bomb. Sitting at a very very very long traffic light on a HOT July afternoon it topped out at 200*. I was boiling in the car. :eek: Once the light turned green and got it rolling, right back down to 190*.

Joe,
Glad to hear the temps came down and stayed there. Just got my tranny cooler in the mail today. Still waiting for the aluminum rad from Summit. Should be here in about a week. Hope I have the same good results as you did. Since it stopped raining down here in Fl the temps and the humidity have been sky high. If it works in this weather it's gonna be great.
Roy