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The problem I have with 220, even if that’s not overheating, is that’s it’s the full sweep of the gauge, so you can’t tell for sure if it’s getting hotter or not.
I had issues with my 60 cruising on the highway. Chased many things ultimately discovered that the vacuum diaphragm was not holding under steady vacuum. Hooked my vacuum pump up to it, pulled 15 in/hg and watched it leak down. Replaced diaphragm and temps all normal again.
Also you mention that your rad is "not clogged". How can you be sure of that unless you can check each row of tubes. Can't do that with the tanks on....?
When replacing the rad Dewitts is the way to go. I've put several into different Corvettes and none have issues. They may be more expensive then others but worth it.
I wouldn't drive mine at 220 very much. I can't say what's different on yours, but I put a C2 style 5 blade fan with a clutch fan instead of the stock mechanical 4 blade fan, changed the vacuum advance to the correct one for the 2" rule for advance, connected the vacuum advance tube to the hollow mounting screw on the driver's side rear of carb base(manifold vacuum), and having the radiator boiled out. Your car may or may not have the hollow bolt, but either way it needs to be connected to full time manifold vacuum.
Getting hot at highway speeds will be in radiator or coolant flow. GM says they are not overheating unless they puke. Timing too much before TDC can contribute.
They came with copper radiators, you can have them cleaned out. Bad airflow or bad coolant flow will probably be your problem, if you have one.
This is an inescapable fact that still has many running in circles addressing everything but the issue. If you can confirm its really overheating as opposed to a 63 year old gauge and sender being wrong, and it overheats on the highway the maxim above applies, every time. I would look at my water pump impeller and check for rusted and blocked coolant passages before I condemned the radiator. I have the original, stock brass Harrison radiator in a 60,000 mile Buick Electra. Still on the job.
This picture shows the routing to my carb base hollow bolt that the vacuum advance connects to. I would like to add that I did all that because mine got hot at idle and sometimes puked. I also added a $10 plastic coolant recycle bottle to the overflow tube on the radiator and hid it behind the front bumper brace in front of the passenger front tire. If any coolant comes out into the bottle, it will theoretically pull it back in when it cools. Since the changes, the level in the bottle doesn't change.
I have the vacuum advance connected to the intake vacuum (I made a hollow stud), that is something I know needs to be done.
I was curious if the gauge will read higher than 220 or if it stops there.
My radiator could be restricted some, as it is hard to see, but I had another radiator in it before that is a new old stock Eskimo that is a weird cross flow design but is set up to not use a surge tank (similar to the late 50s design). It's definitely clean inside, and the car ran hot with that one too. They both dump water out quickly when playing with a garden hose, with the radiator out of the car.
If you have a correctly operating 180* T-stat, your coolant should be at 180*.
For fail safe reasons, i drilled two 1/8" holes in my T-stat body, if the ambient temp is less than 65*F, the gauge only reads about 165-175. Over 75 outside, it reads 180*, and stays there unless it gets to over 100F out, in which case it will read 190-195 at 105-110 ambient.
DeWitts alum resto radiator, correct fan shroud, 7 blade LS 6 fan, Eaton fan clutch and 427 CI small block.
07-09-2023, 08:44 AM
