3. What do you recommend for minimum/ maximum engine-operating temperatures?
Be CoolDepends 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-liteThe 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.
GriffinToday'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'sThe 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.
WalkerMinimum 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 CoolInternal 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-liteNot 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.
GriffinIf 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. RadiatorExternal transmission coolers are preferred to keep unnecessary heat out of theradiator.
WalkerA 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.