3. What do you recommend for minimum/ maximum engine-operating temperatures?
Be Cool
Depends on application (i.e., electronic fuel injection/carbureted). Most engines operate at 180 to 210 degrees Fahrenheit. This temperature range is suitable for most street applications.
Flex-a-lite
The thermostat or restrictor plate that is installed in the engine determines engine-operating temperatures. Some fluctuations in temp will occur due to load and outside ambient temperature changes.
Griffin
Today's late-model fuel-injected engines are designed to run at least 10 degrees hotter than earlier-model carbureted V-8s. A safe range is 185 to 210 degrees at idle and 185 to 200 degrees while moving. You want the engine to get hot enough to evaporate any moisture that may have accumulated inside of the oil system.
Mattson's
The engine manufacturer always suggests an operating temperature. The late-model engines are running hotter and hotter. What used to be hot is now considered too cold in some applications. Some systems with fuel injection do not operate correctly at lower temperatures. We always suggest engine manufacturer guidelines.
U.S. RadiatorMost hobbyists aren't concerned with fuel efficiency, so our recommendation would be 175 to 195 degrees. Higher operating temps will burn fuel more efficiently, but the increase in operating pressure and metal distortion can easily create problems over time.
Walker
Minimum and maximum recommended engine temperature range varies. Engines up to the mid-'80s normally had a range of 180- to 200-degrees operating temperature. The late '80s to the present have a range of 195 to 220 degrees Fahrenheit.
4. Do you recommend internal or external automatic transmission coolers?
Be Cool
Internal transmission coolers are sufficient for normal driving conditions. External transmission coolers are needed for towing, race conditions, or when the addition of heat to the radiator is not desired.
Flex-a-lite
Not all radiators are built with internal transmission and engine oil coolers. In these applications, the use of the external oil cooler would be required. In most cases, the external oil cooler will excel over the smaller internal coolers.
In extreme cold-weather areas of the country (approximately 20 degrees Fahrenheit and below), the use of the internal oil cooler would be necessary to keep the oil heated, allowing it to flow more readily. It can then be run through an auxiliary cooler mounted in front of the radiator. Most new-style, synthetic fluids will still flow under the above temp. The use of an external cooler with this style fluid would then be OK.
Griffin
If the stock converter is used, then an internal transmission cooler is fine. If a high-stall converter is used, then we recommend the use of an external cooler. The external cooler can be used in conjunction with the transmission cooler in the radiator.
Mattson's
Transmission coolers can do a terrific job inside the radiator. You can always add an external cooler if you have a special application like a high-stall or towing application. The one issue with a cooler is that it is in front of the radiator so it's an airflow obstruction. There is added heat blowing through the radiator, and the transmission cooler inside the tank creates additional heat inside the radiator. The difference is probably so minimal that it doesn't matter; however, being in the radiator provides for a cleaner look and a chance to add an additional cooler if needed. If you get down to it, an under-the-car cooler with a fan on it would be ultimate, except for the extra wiring and road debris that may affect it.
U.S. Radiator
External transmission coolers are preferred to keep unnecessary heat out of theradiator.
Walker
A proper-sized internal cooler works well for normal driving. A proper-sized external cooler working in conjunction with the internal cooler is a must for cars pulling trailers or performance transmissions with high-rpm stall speeds.
5. How does radiator core thickness affect cooling?
Be Cool
Increasing core thickness slightly increases cooling capacity. It should be noted that increasing frontal area is a more efficient means of increasing cooling.
Flex-a-lite
In vehicles with the belt-driven fan option, the thickness would not be as much of a factor in cooling as the electric would. Electric fans, when installed, will require a minimal static load, blockage, in front of it. In the event a "multicore" radiator is used, it may cause a reduction in the cfm that the electric fan can pull through the core. Too much static load will reduce the effective cfm to a point where it will not cool the application.
Griffin
Cfm is too low with a thick core (more than 2.25 inches) and the fan, so you then run the risk of the radiator not cooling properly at idle.
Mattson's
The air will have a hard time cooling off the radiator if the radiator is too thick. Some of the old continuous fin-type cores were great for the dirt roads and minimal traffic a long time ago.
U.S. Radiator
An increase in thickness over a stock application allows for greater fin bond surface and therefore greater temperature drop. When going from a two-row to a four-row, for example, you double the fin bond or heat transfer points. However, the increase isn't a one-to-one because the transfer efficiency of the trailing rows is adversely affected by the increase in air temperature from the previous rows and the decrease in air velocity caused by the increased thickness.
Walker
The key to all cooling is determined by the prime cooling area. The prime cooling area is the frontal core area and the prime cooling area of the core is the first 1 inch. This is the area where the radiator fin's design and the air management package are critical. Doubling the thickness of a radiator results in only 20 percent more cooling efficiency.
6. How does fin count affect cooling?
Be Cool
Increasing fin count will increase the capacity to reject heat, up to a point. If the fin spacing becomes too close, the airflow can become restricted and may reduce cooling capacity. OE radiators use 18 to 20 fins per inch. Be Cool has proven that its 14-fin-per-inch design is the most efficient for air travel with the least resistance.
Flex-a-lite
Theoretically, the more fins per square inch a radiator has, the better it will cool. More fins will provide more surface area to dissipate heat. Reality is that the number of fins and the angle of the fins can affect the ability of the cooling fan to move the air through it.
Griffin
Same effect-you can run a thin core with a high fin count, or you can run a thicker core with lower fin count.
Mattson's
The type of fin and the number of fins per inch determine the efficiency. The type or too many or few fins affect the proper efficiency.
U.S. Radiator
We've found that core design, and not material, had the greatest effect on temperature drop. While all radiator cores might look the same, they perform vastly different based on tube spacing and fins per inch. Heat transfer points where temperature is actually allowed to leave the radiator are where the fin is bonded to the tube. The more transfer points, the greater the temperature drop. A '60s core, for example, had a 1/2-inch tube spacing (i.e., 1/2-inch fin between the tubes), and by going from a two-row radiator to a four-row core design, we were able to double the heat transfer points, which resulted in a 15 to 20 percent increase in temperature drop without changing the other variables (airflow, coolant flow). In the '80s, the Japanese came out with a core design in response to the need to downsize that has become the standard and was efficient enough to allow the re-introduction of aluminum (a less efficient heat transfer material) at the OE level. By changing the tube spacing to 3/8-inch, a design referred to as High Efficiency in the industry, more tubes or water passages and fin were allowed across the face of a core with a specific width in inches. The design was simple enough but proved to be very efficient in that more heat transfer points created greater temperature drops inlet to outlet.
Walker
Fin count (number of fins in a given inch within the core area) affects the number of times a fin-to-tube contact is made. The more fins per inch you have, the better the heat transfer (up to a point). Too high of a fin count will cause an air blockage, limiting the core's cooling performance.