Choosing a replacement radiator.August 8, 2018
A typical scenario goes like this: An engine in a farm machine or truck needs a new radiator and is beginning to run hot. You shop around and find a wide discrepancy in price and decide on the least expensive replacement. You are pleasantly surprised that it bolts right in and all of the holes, connections and fittings are right where they should be. You are proud of your wise financial decision… that is until you start to work the engine and it runs just as hot or even slightly hotter than with the old radiator. How can this be? Is there something else wrong with the engine? It can’t be the radiator, right?
The job of the liquid is to cool the engine and it is the radiator’s task to cool the liquid. To do this properly it must be designed for the Btu rejection of the engine. Just because it fits in place has nothing to do with how it performs. That is referred to as fitment.
Factors that impact heat rejection
A radiator consists of the tanks, headers and core. It is the core that has the most influence on its efficiency.
Heated coolant is circulated through the core. There small quantities of coolant travel through the tubes that have fins attached to them. This is where the heat transfer from the liquid to the air occurs. The design of the tubes and fins are paramount to this.
Specifications such as fin density per square inch, the size and shape of the tubes and fins, whether or not a device is added to induce turbulent flow in the tube (very desirable) along with the material used to attach the fins and if they go to the end of the core and butt up against the tank, all add up to making the radiator efficient. Some of these things you can see but many you cannot.
A simple equation for heat rejection required by a radiator is: Btu/min required = 0.65 X HP X 42.2. A 350 HP engine would require a radiator that has the ability to dissipate approximately 9,600 Btu/min to keep the engine cool under a load.
The best choice is to buy a factory replacement. It will have the heat rejection requirement for that engine. It will cost more but it will work as designed.
There are excellent aftermarket brands that produce the same heat rejection as the factory unit. Historically, the lowest cost unit employs an inefficient core that they use for every part number in their catalog and is cut to size. Often the same core is employed on a 90 horsepower economy car as on a 400 HP tractor. That is how they come to market so inexpensively. They make the sale but your engine pays the price!