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Down Flow Radiator

The Torana down flow core is approximately W 650 mm x H 360 mm (2340 cm2). This means you are limited to twin 12” ( 300 mm ) fans or a single 14" ( 350 mm ) fan if you want to stay within the core boundary. A 16” ( 400 mm ) fan can be fitted but it will overhang the core. If you have a manual then you could line the 16" ( 400 mm ) fan up with the top of the core and let it overhang at the bottom of the radiator. This may not be an option with an internal transmission cooler as the fan may foul on the transmission cooler lines.

Cross Flow Radiator

The Torana cross flow core is approximately W 470 mm x H 520 mm (2444 cm2). Twin 12" ( 300 mm ) fans will overhang the tanks and not cover the core effectively. A single 16" ( 400 mm ) fan will fit nicely on a cross flow core, this in my opinion is the main reason to fit a cross flow radiator in a Torana. The downside is that the cross flow design does not expose as much core area to direct airflow as the down flow design in a Torana.

The main advantage of a cross flow radiator verses a down flow radiator in terms of design is that the radiator cap on a cross flow radiator is located on the low pressure (suction) side of the system, so it is unaffected by the pressure generated by the water pump. Down flow radiators have been know to have problems with the radiator cap leaking into the overflow at high rpm.

Airflow

There is considerable debate as to how much airflow is required. Engine modifications, automatic transmissions, hi-stall convertors, transmission coolers, oil coolers and A/C evaporators all add to the load. The local climate and traffic conditions should also be considered. In Perth I would consider 2300 cfm a good starting point. If the car is going to be driven in heavy traffic on a 45 degree day then 2300 cfm will not be enough.

As a general rule of thumb it appears that an 12 volt electric fan can produce between 100 and 150 cfm per 1 amp current draw. Zirgo claim their 16” fans produces 3000 cfm and draws 10 amps. SPAL claim their high performance 16” fan produces around 3000 cfm and draws 20 amps. I find the Zirgo cfm claim dubious.

Typically the alternator will need to be upgraded to a minimum of 85 amps to handle the load created by the cooling fans.

SPAL 16" on a cross flow radiator

There are several 16" SPAL fans rated between 2350 cfm and the extreme which is rated at around 3000 cfm. The SPAL extreme does not have a sealed motor and is not recommended for street use.

AU Falcon fans on a down flow radiator

The best value for money option is AU Falcon fans. Unfortunately the lip near the chassis rail needs to be trimmed to make them fit. I have also heard of people squashing the shroud between the lips on the chassis rails and trimming the blades of the fans so they do not touch the shroud. I have been told that each AU fan is rated around 1900 cfm and draw 20 amps. The AU fans cost around $250 for factory fans with Bosch motors. There are aftermarket copies available however they doe not used the same motor and are not as powerful. The brackets are cut off the fan shroud and 12 mm is trimmed from the depth of the shroud to move the fans closer to the radiator. The fans are mounted upside down on a V8 Holden radiator and the right way up on a Chev radiator.

Ford Mondeo fans on a down flow radiator

The Ford Mondeo fans will fit without modification to the chassis rail lips. They are more expensive than AU fans and not as powerful. I have seen Ford Mondeo fans sold on eBay now and then as "Twin Shrouded Thermo Fan" for between $150 and $200. They may just be copies with inferior motors like the AU Falcon copies or they could be OEM.

Twin Derale 16926 on a down flow radiator

I have twin Derale 16926 fans on an aluminium shroud. Each fan is rated at 2200 cfm and draws 23.4 amps. The Derale fans appear to use the same motor as the AU fan (Bosch) and a similar blade design.

SPAL Fan Controller

The SPAL fan controller FAN-PWM-V3 can be used to control one or two fans. It has an input that can be connected to an A/C circuit to trigger the fans when the A/C compressor is running. The fan controller can read some factory temperature senders or use its own sender. You can configure low and high temperature settings in the controller. When the low temperature is reached the main fan is switched on at low speed. If the temperature continues to rise the fan speed is increased. Once the high temperature setting is reached the main fan is at full speed and the secondary fan relay is triggered.

Painless Performance F5 Fan Dual Fan Controller P/N 30140

The F5 fan controller has the same features as the SPAL fan controller with the addition of a speed sensor allows you to specify a speed at which the fans will turn off.

The F5 Dual Fan Controller is rated to control two 35 Amp cooling fans. Controller features include dual cooling fan control from 50% up to 100%; A/C compressor override that runs the fans at 100% duty cycle if air conditioning is kicked on. Kit also includes a three position toggle switch that gives you manual control of the cooling fans; position one is 100% fan on, position two is normal operation and position three is 0% fan or fan off. Also included is a push button switch which is used to set the vehicle speed at which you like the cooling fans to shut off above.

Transmission Coolers

There are four basic options for transmission coolers.

1. Internal transmission cooler mounted in the bottom tank for the radiator. This is the simplest method and requires the least space. It is typically not considered suitable for towing or high stall torque convertors. The major downside is that if the internal cooler ruptures then coolant will mix with transmission fluid and destroy the transmission.
2. External booster cooler. The internal transmission cooler is used in conjunction with a small external cooler. Factory towing packs will typically include an external transmission cooler to be used in conjunction with the standard internal cooler.
3. Stand alone external cooler.
4. Stand alone external cooler with thermostatically controlled fan.

The following is an interesting quote from the Performance Automotive and Transmission Centre on the subject of transmission cooling.

You must have a transmission cooler in your radiator regardless of what someone has told you for the transmission to last. Auxiliary coolers are just that, in addition to. Water cools 32 times better (faster) than air always, period. In the case of air vs. water, there is no contest - water is way better. The transmission fluid comes directly from the torque converter at a much higher temperature than the water in your radiator and is cooled to the water temperature fast. Then it goes to the auxiliary cooler to be cooled far below the water temperature. If you don't need a cooler in your radiator why does GM spend all that money doing so? If you wanted to cool a red hot piece of steel fast would you stick it in water or air, see the point. Your transmission will run cooler with a lock-up converter. This is more important with stall speeds of 2000 RPM or higher. For the best cooling you need both water and air cooling for the transmission to be cooler than the motor (water).

Coolant Filters

If you have a iron block then a radiator filter is a must.

Clean Flow Radiator Filter Sock

Tefba Radiator Filter

Radiator Links

Stewart Components Tech Tips 1-5

Aluminium vs. Copper Radiators

Top Ten Cooling Suggestions For Your Rod