I have problems at Highway speeds of the car over heating. I have a extra transmission cooler. And I have looked a the water pump and a high flow thermostat I have no leaks or pressure problems. 68 40 0 convertible

This has been covered alot here. Look here for some good reading... Over heating

Over heating2

Timing

Kel

1st , do you have all the fillers? the X fillers, the rubberized masticated fillers at the bottom sides of radiator and the lower baffle? if so try the waterpump modification....
its on some of the stuff Kelly listed above ,but here`s a compilation...
I am about to do this myself next two weeks... web page
I think it will work!

I had a similar high speed cooling problem as I have a 400 convertible with air conditioning. It turns out that my car was missing the lower air baffle valence like Bjorn mentions above. It lays flat under the car and connects to the front valence routing air into the radiator. Without this, it's easy to see how air would pass under the car vs. thru the radiator. My understanding is that only original 400 cars or air conditioned cars came with these. I also think that many could have been left off by repair shops, etc.

I bought a fiberglass version from Ames ($99) and installed it. The fit was good along the front but the two tabs in the back were very mis-aligned and required some serious work to attach. The car does run cooler at highway speeds now. Does your car have this? It's flat with a 90 degree bend in it. I couldn't find an original so I had to get the fiberglass version.

The previous owner of my bird obviously did a lot of things to try to cool the car. These included adding an electric fan, eliminating the heater core from the cooling loop and removing the thermostat. I changed all of these things back to original but nothing really helped until I added the valence.

Dave

Thanks for your help. This tells me I am going in the right direction I will have to order a lower valance for my bird.

MM

That's weird. My 400 runs cool at speed and only gets hot in traffic on hot days. I don't have any of the fillers or baffles. Could be a bad fan clutch if you have one. I have a flex fan with no clutch. Why would a car overheat when air is going really fast through the radiator at speed? Is your vac adv hooked up and working correctly? This increases timing during cruise and thus keeps the engine cooler. Just a thought.

I can run my AC in traffic without overheating on my 400. NOTHING special, didn't adjust the water pump divider, stock 19" clutch fan, 180 t-stat, stock radiator with trans cooler, currently running stock distributor with points. All the metal baffles and valence are in place, although I can't find any sign of the mysterious masticated fillers So I think the baffles are important for increasing the fan's efficiency at low speed. I agree, check your vacuum advance and distributor mechanical advance for proper operation, and the advance curve to make sure it's coming in on time for your gear ratio.

If you're overheating at highway speeds the solution is obvious. You're driving too slow! Speed up! Force more air through that radiator!

- Jake