Internal combustion engines are designed to run “hot” in order to run with some semblance of efficiency. If you have an engine that runs too cool, You could develop issues like inefficient combustion, and condensation forming inside the engine. Get your mill too hot, and you know what can happen. But is there an ideal engine operating temperature? Most professionals agree that 190 to 200 degrees is a good temperature range to shoot for.
Phil Sanner of Lakeland, Florida felt the engine in his ’71 Nova was running hotter than it should. In fact, according to the aftermarket gauge, it would climb to the 220- to 230-degree range while sitting at a red light in the Florida traffic. It would immediately come back to normal when he started driving. He asked for some suggestions, wanting to know how he should upgrade his cooling system. Before we simply started to replace parts, we reached out to the folks at Champion Cooling to get some help from people who know cooling systems.
Why do most professionals agree that an ideal engine operating temperature is roughly 190 to 200 degrees? That’s hot enough to boil off moisture and prevent sludging, yet still low enough to provide a cushion in case of heat spikes. Operating temperatures lower than that provide most people a false sense of security, but lower temperatures can result in unnecessary sludging of the oil and may prevent engine/fuel/spark management systems from operating at optimum efficiency or power.
“We often see 195 to 205 degrees for big-block Chevys, but quite often, lower temps in small blocks,” states Michael Harding, director of marketing at Champion. “The thing to keep in mind is that an engine will find its own ‘comfortable’ operating temperature and throwing parts at it — like an aluminum radiator — isn’t necessarily going to change that. While an aluminum radiator can drop the temps a little in a properly operating cooling system, many times the myth is that swapping to an aluminum radiator will automatically do so. If there’s an overheating issue, it may do very little at all until you find and fix the problem.”
A properly working pressurized system (13 to 16 psi), with a 50/50 mix of antifreeze and water can safely go to 260 degrees without causing engine damage from heat alone. The key is to not lose coolant. Loss of coolant can result in hot spots, vapor pockets, warped heads, etc. However, 230 degrees and above can change the spark map required to prevent engine damage from pre-ignition/detonation. Most factory ECM spark-controlled engines automatically reduce spark advance as coolant temp increases. Mechanical distributors or non-ECM-controlled engines do not have that advantage and have problems with detonation at higher engine temperatures, and that can cause damage.
Before we get too deep into the cooling discussion about Phil’s Nova, a few details need to be brought to light. For one, Phil only recently purchased the Nova, and although the engine is strong and runs great, he really has no information about how it is put together. What he does notice is the temperature gauge running higher than he would like when sitting in traffic in the Florida summer. But why?
A Coolant Filter?
Why do you need to consider a coolant filter? Have you looked at your coolant lately? Okay, maybe it’s not as bad as chocolate syrup flowing through the system, but regardless of how well-maintained your cooling system is, you will still have a small amount of debris floating through the system. The debris is inevitable and can eventually harm or plug the radiator, thermostat or water pump.
By adding one of Champion’s in-line coolant filters, you can protect your cooling system from rust and other debris. As the coolant flows through the filter, it is caught in the removable and reuseable filter screen, keeping your water jackets clear and your engine cool.
When these older cars came off the assembly line — in stock form — they didn’t typically have an overheating problem. General Motors put a lot of effort into ensuring that the original purchaser did not have to be concerned with an overheating engine. But here we are, 50 years and a multitude of modifications later, and it can now be an issue.
Determining An Issue And The Remedy
There are many issues that can cause an engine to overheat. If you are running too much or even too little ignition timing, your engine can overheat. If your air/fuel ratio is too lean, your engine will overheat. If your thermostat is sticking, your engine will overheat. If your fan is not running, your engine will overheat. If your radiator is not efficient, you surely realize that your engine will overheat. What this means, is you really need to make sure everything else is as it should be, or replacing the radiator might not cure your issue.
“One issue about how ignition timing and air/fuel ratio can affect temperature is, if those are the factors causing higher temps, it’s usually more noticeable because the engine is running poorly,” says Harding. “It’s rare that your engine is overheating because of poor ignition timing if the engine is running at its best, so the two really go hand in hand. Out here in California, running 8 degrees BTDC isn’t going to cut it with the fuels we have. Setting the ignition timing a little higher does help, and in order to get roughly 14 to 18 degrees of base timing and maintain a 34 degrees total timing, a distributor recurving might be needed.”
With these parameters in mind, Phil first ensured the electric fan was pulling a sufficient amount of air through the radiator. We placed a piece of standard-sized legal paper in front of the radiator and verified sufficient airflow as the paper was pulled against the radiator.
Next, we decided to swap out the thermostat. He purchased a 185-degree unit to replace the 195-degree “flow controller” under the housing. He took the car for a ride, and according to the temperature gauge, he saw no noticeable change in the car’s temperature spike.
With that not making any noticeable change, we decided to take a look at the ignition timing. This is the easiest aspect to check and once we made sure the timing was where it needed to be, the car was again driven around the block. Unfortunately, as soon as we came upon a red light, the temperature started to rise once again.
We got the car back home and gave it another once over and decided the current radiator was not efficient enough to effectively cool his small block. Although a cursory look inside revealed no real blockage or any other issues, the radiator wasn’t sufficiently doing its job.
Making The Most Informed Choice
This is when we decided it was time to reach out to someone that knows cooling, and called the tech line at Champion Cooling. One of the first things we needed to do was answer a few questions about the car and its intended purpose. We explained the current radiator has three cores that carry coolant but were surprised to hear that could be an issue if the cores are not the proper size? Yep, we were as confused as you are right now.
According to Scott Simison at Champion, “When I am discussing this exact concept with customers, I usually begin by asking them an important question that may have some impact on which design I think will be the best fit for them. That question is, what kind of water pump they are using and if they can provide me the flow rate of said water pump. This is important because, if a customer is using a high-flow water pump and wants to use a radiator with a larger tube diameter; for example, a two-row with 1-inch tubes, then they could very easily find themselves having cooling issues. At that point, they may feel the radiator itself is not sufficient when in reality they are simply moving fluid through the radiator too quickly.”
In short, some applications could find a greater benefit using more smaller tubes while others could find increased benefit with fewer larger tubes. The only way to make sure you get it right the first time is to call and talk to one of the professionals.”
When it comes to radiator design, there are actually a couple of options available. First is the single-pass radiator. This design allows the flow of coolant to pass through the radiator one time. Single-pass radiators have coolant flow from the inlet on one side to the outlet on the other side.
With a double-pass radiator, coolant flows through the radiator twice before returning to the engine. The inlet and outlet of a double-pass radiator will be on the same side. As the coolant enters the radiator, it flows to the other side and is then directed to flow back through the lower half of the radiator. Since the inlet and outlet are on the same side of the radiator, connecting the upper radiator hose can be an issue. An easy way to make the upper hose connection is to use a pivoting thermostat housing and a new hose.
A triple-pass radiator has coolant pass through, you guessed it, three times. Triple-pass radiators are more suited for race applications. Inlets and outlets will usually be on opposite sides and the flow will pass through the core three times. High-volume water pumps, little to no restriction, and 1-to-1-ratio pulleys are basically a requirement in order to ensure optimal circulation and cooling effect.
With three options available, how do you know which is actually best for your application? “There are only a handful of questions that should be asked of the customer to get an overall sense of which version of a radiator the customer should buy,” says Scott. “The first considerations are what type of engine is being used and how much clearance they have from the core support (or saddle mounts) to the engine. The clearance between a V8 and a straight-six can be substantial. The size of the engine may also warrant a thicker core, simply based on the need for increased fluid volume. Another consideration is whether they are using OEM mounting points or looking for a custom-fit unit.”
“The next question is what type of cooling fans are they planning to use,” Scott iterates. “This is an important question, because, with mechanical fans, it may further limit the available clearance the customer has to work with and force them into a thinner core, solely based on that. This problem can also occur with electric fans, as the radiator, shroud and fan could create an overall thickness of the kit that is too great for the customer’s overall available space.”
Thankfully, there are many thickness options available for electric cooling fans to counter this problem. It should be noted however that most of the time you are sacrificing fan power to reduce its overall thickness (i.e., low-profile fans). Air resistance can be made better or worse based on the thickness of the radiator core alone, and that is before you factor in other potential negative airflow barriers like A/C condensers, flat-plate-style external engine oil/transmission coolers or any other items that can be mounted in front of your cooling system.
Finally, we asked Scott if fin count and design really matter when designing a radiator. “Fin count and design do matter,” he exclaims. “However, it does not matter as much as airflow itself. This is because proper fin design can make the airflow more efficient from all sources. With any radiator, you want the fins to maximize the flow of air out and away from the radiator because that flow of air is what is pushing the heat out and away. I tell customers that it doesn’t matter how big your radiator is, if you’re not moving air through it, you’re dead in the water. You want the fins to improve the flow of air instead of obstructing it.”
Unfortunately, there is no one-size-fits-all cooling system design with the very wide range of applications the folks at Champion Cooling work with on a daily basis. In other words, before you buy a new radiator, you can really help ensure you get exactly what you need by first making a phone call and know for certain the radiator that arrives at your door is the best option for your application.