Every engine combination has a specific cooling requirement for the size of the engine, the amount of horsepower it produces, and its desired operating range. But, the real world is different than the theoretical one, and there are compromises dictated by available space that often need to be made along the way. For example, if you are swapping an LS engine into a Miata, there’s not much space for a large radiator, so you have to dig into your bag of tricks, and use more cooling system options such as electric fans and expansion tanks.
On the flip side, if you’re dropping a big-block into a classic muscle car, space is less of a concern. Still, you may also want to have a clean look to go with the new speed goodies you’ve added, such as valve covers, accessories, aluminum radiator, and so on. You shouldn’t discount the need to plan out your cooling system just because you have more room for a larger radiator.
Expansion and recovery tanks are typically mounted at the highest point in the cooling system to let out air and allow for thermal expansion of the fluids when it heats up. In performance applications like racing, the overflow tank is just an overflow of your expansion that acts as a catch can. Or you can also set it up as a recovery system, which will suck the coolant back into the expansion tank once it cools off. When the coolant is in the recovery tank, it’s not pressurized as it is in the expansion tank.
The recovery tank cap is vented to the atmosphere. But once it cools down, it creates a vacuum, where it’s going to suck back into the court system once it cools off. — Iann Criscuolo, Canton Racing
While expansion and recovery tanks work together, they each have a different purpose. “We have a lot of customers that use both an expansion tank and a recovery tank.
Criscuolo says you need to keep a few things in mind when building your cooling system. First of all, there’s a formula that is used to calculate the correct size (or the minimum size) of the expansion tank. “We offer many different sizes of tanks, depending on your needs. We have a universal tank for custom setups, and we also have model-specific tanks. But generally, we follow specific guidelines when it comes to sizing. For example, the drawdown is when the core is completely cooled down, and the coolant returns to the normal level at normal ambient temperature. We calculate that you need 12-percent of your total coolant system capacity. And then you also need a tank that has at least 6-percent of the core size as it expands at 212-degrees-Fahrenheit operating temperature.”
Criscuolo says that the 12-percent and 6-percent (of your system capacity) numbers are added together to give you the required expansion tank size. “I’ll give you an example,” he explains. “Let’s say you have a 13-quart system capacity in your vehicle now after you added a power adder, and you set up your cooling system how you want and know where you want your expansion tank placed. At 12-percent drawdown, you would need 1.56 quarts, and for the thermal expansion, you would need 0.78 quart, which will equate to 2.34-quarts. That’s the smallest size you can get by with for your system, and that’s how it should be calculated for any size system.”
The OEMs didn’t use an expansion tank for some older vehicles. There was only a radiator with an overflow port in the neck that would dump out into an overflow tank, which would be the recovery tank. However, on newer production vehicles, the OEMs use plastic or polycarbonate for the recovery tank.
“[Plastic] is not the best choice for use with extremely high temperatures because the material breaks down and they are prone to cracking. I have experienced this issue personally on my BMW 330 CI. — Iann Criscuolo.
Criscuolo cautions that if you’re upgrading different components in your vehicle, like putting new heads on, or adding a supercharger, or a turbo, you should probably spend a little extra money also beefing up the cooling system to something more robust. “You don’t really want to have a lot of plastic, especially since your core temperatures now are going to be higher in your cooling system, because you’re pushing the vehicle harder. Our tanks are aluminum TIG-welded, as opposed to the stock OEM plastic, which is not well suited for racing use or even hard street use.”
If you’re building a performance application, usually bigger is better when it comes to radiator sizing. However, in some cases, like with engine swaps, you may not have the space for a large radiator and other accessories under the hood. “You might have to finagle some things around,” says Criscuolo. “And, you may not be able to get away with a gigantic radiator (due to space). Keep in mind that the bigger the radiator, the more capacity will be needed in an expansion tank. Another thing to keep in mind is if you place the radiator somewhere else that is lower than the engine, then you will need an expansion tank to compensate.”
Canton’s expansion tanks are pressurized and include standard caps in 16 psi and 21 psi. Criscuolo says you can go up to 30 psi, depending on your requirements. A bigger expansion tank can handle more drawdown and thermal expansion, so you may not have to worry about having a recovery tank as well. But, depending on your setup, you might have a space issue if you need to place your expansion tank at the highest point, according to Criscuolo. “If [the expansion tank]is too big (or too tall), there may be an issue with hitting the hood. By using a smaller tank with a recovery setup, you could have room for expansion and then any overflow with the recovery tank lower than the expansion tank. That’s one of the benefits.”
There are a lot of options with recovery tank sizes and configurations. Canton Racing offers them together in one compact package or separately, so you can get the most out of the available space and place the tanks where you want them. “If you just have a very large [expansion] tank, you may not need all of it for expansion, so it’s a bit of a waste of space,” Criscuolo adds. “As long as you go with that recommended equation we talked about earlier — 12-percent and 6-percent — any more than that is a waste of engine bay space.
Criscuolo notes that you can also add a sight gauge to the recovery tanks (but not the expansion tanks) to see how much the coolant expanded on the recovery side. “A lot of drifters use these setups. They put the recovery tank in the back of the vehicle where the trunk would be, and they can easily top them off and take a look without having to open up the hood.”
Criscuolo also mentions that Canton Racing can build racers and hot rodders custom tanks. So, if you need a custom size or shape, they can be custom-fabricated to your specifications. You can also use different style caps for the expansion and recovery tanks. Canton offers a fuel-style cap for some of their supercharger tanks. “We have a new one which is a 2011-through-2014 GT 500 supercharger tank that has a fuel-style cap and a pressure relief valve. We do offer different styles and different sizes. If anyone wants anything custom, we have a custom department that customers can reach out to as well.”
If you are looking to upgrade your cooling system or do an engine swap, don’t forget to factor in a performance expansion and recovery tank. Besides the great looks of the tanks — which come in crinkle finish black matte and aluminum – they are a lot more robust than your cheap OEM plastic tank that is one or two heat cycles away from cracking and the plastic recovery tank that is already discolored. So if you’ve invested in a new aluminum radiator and added on some extra horsepower bits, it’ll be worth the additional cost to ensure your ride performs as well as it looks. And if you’re going to be using your car for any kind of performance, you want premium products that will last.