It's amazing how many homebuilt cars—as well as a few professionally built ones—suffer from cooling issues, whether it be full-blown overheating or simply running too hot. There can be any number of reasons for this, though more often than not it's caused by the radiator simply not being up to the task at hand, closely followed by the fan, or fans, not moving enough air through the radiator core.

We had a couple of cars with different problems, our '46 Ford roadster pickup, and a friend's '63 Chevy Nova wagon. The latter had received a GMPP crate 350 in place of the stock six a couple years ago, with a new water pump and radiator to match. However, in the heat of the summer it was noticed that the wagon had started to run a little warmer than what had been a 195-degree norm, especially in rush-hour traffic, more than once requiring exiting the freeway to cool down. With all-new parts used during the conversion, the cause was a mystery. Rather than take a shot in the dark by replacing parts one by one (though admittedly this would have answered the question of why the wagon was overheating), our buddy sought the advice of an expert, namely Don Armstrong , owner of U.S. Radiator.

After checking out the wagon, Armstrong suggested the following: remove the plastic low-flow flex fan and replace it with a high flow and more efficient 17-inch, seven-blade fan, switch the 180-degree thermostat for a 160-degree version, replace the radiator with a copper/brass version with a high-efficiency four-row core, and fabricate blanking plates to prevent hot engine compartment air from re-circulating over the core support and passing through the radiator, a problem which can happen at idle or low highway speed. We could have gone further and added a fan shroud to the Nova, but found it unnecessary. With these mods done, the wagon once again was running at 170 degrees, whatever the traffic, proving a little solid information can go a long way.

While Armstrong was at our Tech Center inspecting the wagon, we took the opportunity to have him give our pickup the once-over. While it's never let us down (OK, it's overheated a couple of times traversing the infamous "Grapevine" over the mountains north of Los Angeles), and has traveled through many states, its constant hot-running has always been cause for concern, especially on long mountain grades. We knew the radiator was a weakling two-row core, but had persisted with it mainly because it was such a bear to remove and replace! Stupid we know, but with a crossflow radiator mounted so each end tank is under the fenders, the only way to get it out was from underneath, and we'd welded in the crossmember that supported it, in a typical last-minute rush to get the truck running years ago!


1. The radiator removed from the Nova was not only inadequate for the job, but the side plate had come away from the top tank too. This radiator, installed when the V-8 replaced the straight-six, would be replaced by a high-efficiency version from U.S. Radiator.

2. Flex-a-lite's 17-inch seven-blade flex fan is designed to pull air through a three- or four-row radiator, and is quieter in operation than most flex fans, too.

3. Flex-a-lite also supplied a selection of fan spacers to fine-tune the gap between the new flex fan and the radiator core.

4. We added a 16-psi–rated cap to the new radiator.

5. This 160-degree thermostat also came from Flex-a-lite, and replaced the existing 180-degree unit in the Nova.

6. The new copper/brass radiator is similar to what GM used to cool 350hp 327 engines, but with a higher efficiency four-row core. U.S. Radiator can fabricate aluminum or copper/brass versions, but rate the latter for their higher efficiency when comparing like for like.

7. Though we didn't use it on the Nova, high-flow water pumps can sometimes be a help when troubleshooting overheating issues. FlowKooler high-flow water pumps resolve low-speed heating problems by doubling flow rates at low rpm and idle. They can also delay the onset of cavitation at higher rpm.

8. The Nova has an open space between the top of the grille and the core support, which allows hot air from the engine bay to flow up and over the support and into the radiator core at low speeds or when stationary. These blanking plates were made from heavy-duty construction board, having the extra benefit of forcing cool air through the radiator rather than over it at speed.