How To

Hot Rod Cool Down

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by Rick Jensen  More from Author

SPAL Dual 11-Inch Fan Installation

To sit in traffic and watch helplessly as the coolant temp needle inches ever higher is one of the worst feelings in cardom. Whether it is due to a poorly maintained cooling system, a failing thermostat, a coolant leak, or an engine that got modified when the rest of the cooling system stayed stock, it makes no difference: the end result is the same. Excessive temps can be as harmless as the A/C compressor not turning on –and as harmful as a blown-headgasket, engine-damaging nightmare.

Our in-house GM G-body is blessed with a powerful, modified engine – as well as an aftermarket radiator. However, it didn’t take too many commutes in South Florida’s brutal summer heat to uncover a serious flaw: the single cooling fan simply wasn’t up to the task of cooling a built, A/C-equipped mill in high-heat, high-humidity commutes. While the radiator is much more efficient than the stock unit, the stock fan simply can’t flow enough air in environments that routinely see 90-degree temps, and humidity readings over 80 percent.

More airflow was needed quick, so a call was placed to SPAL USA. For over 50 years, SPAL has provided high-performance fans to a host of OEMs, including such high-end makes as Ferrari. SPAL holds an ISO 9001 certification, and prides itself on producing high-quality components that will pass the test of time. So when its products started hitting the performance aftermarket industry, enthusiasts were thrilled.

For a huge cfm increase, we decided on a dual 11-inch fan setup for our overheating hot rod. SPAL was more than happy to discuss some of the technical and fitment questions we had, and soon, the fan assembly was at our doorstep. Cooler temps were just a few hours away – follow along to see how we did it.

1. Here is the factory fan setup. It is fine for a stock vehicle, but not so great for a modified car in Florida heat. Time to upgrade.

2. We started by removing the positive battery cable. Note that this cable is attached to an Optima battery that has been cranking for nearly 10 years!

3. This electric fan is retained with two bottom fan bolts in a bracket, as well as two top fan bracket bolts that are retained by the top radiator plate and some brackets. The two bottom and two top bolts are removed with a wrench.

4. Next, the top bracket bolts are removed.

5. The main fan harness toward the bottom of the fan is disconnected.

6. With a little massaging of the A/C lines, the factory fan is pulled up and out.

7. Replacing it is SPAL’s Dual 11-inch Paddle Blade High Performance Fan (part No. 30102052). Weighing in at only 10.75 pounds, this puppy packs a punch.

8. An up-close look at the SPAL motors driving the fans. These SPAL units have an IP68 rating, so the motors are dust- and waterproof. Note the quality motor and wiring assembly.

9. Here is the stock single fan and the dual-fan SPAL– it only takes one look to see the size difference. The SPAL puts out a whopping 2,720 cfm!

10. Though the brackets will probably not line up based on the Spal’s different mounting holes, they are bolted up for measurement purposes.

11. SPAL offers fan relay harnesses (part No. FRH) for its fans; however, a vehicle-specific piece from G-body specialist Casper’s Electronics was used in this car. Casper’s offers harnesses that are plug-and-play, and also utilize sealed connectors. This harness for running a SPAL dual-fan setup has two sealed, 30-amp relays to handle the power load, as well as a delay module that separates both fans’ initial startup by about a second, lessening the shock to an electrical system only built for one fan.

12. For a clean installation, the two relays and the delay module were mounted in a flat location at the top of the fan assembly. Both fans will run in this car’s computer-commanded, low- and high-speed fan settings.

13. The harness was then routed around the fan housing, and retained with a couple of black zip ties so it wouldn’t stick out too much. Note the large, black connector at the bottom; in this location it will have more than enough slack to reach the factory fan plug. The red wire heading off to the right is the relay feed wire that connects to the battery.

14. As previously mentioned, our Optima RedTop battery has been fantastic for all these years. However, based on upgrades like this fan and possibly a stereo system, we’ll be replacing it with – you guessed it – another Optima. Model D34/78 is a high-performance, dual-purpose YellowTop with premium cranking power and unparalleled rechargeability. This battery has 750 cold cranking amps, as well as 870 cranking amps. It offers low internal resistance, for more consistent power output and faster recharges. We have no doubts that this sucker will last awhile too!

15. With that big YellowTop in the engine bay, it’s finally time to drop the SPAL fans in. The upper radiator hose is disconnected and the A/C lines are tweaked for clearance, as this setup is much wider. Then, the SPAL fans are carefully slid into place behind the radiator. Tip: use a piece of cardboard over the back of the rad to avoid gouging it when the fans are slipped in.

16. Casper’s provides a spacer and elongated battery terminal bolt that work together to provide a mounting point for the fan relay feed wire. The wire is slipped into place and tightened down.

17. The radiator hose is reinstalled, and the main and two fan connections are made. Though the fans were bolted into place using some of the existing brackets, bolts, and a couple of zip ties, they will require a custom bracket for an OEM-quality fit. While that will happen after this issue goes to print, it didn’t stop us from getting before and after coolant temp numbers. Result? The SPAL setup dropped operating temps by 25 degrees!


Our story illustrates the need for a fan upgrade due to increased coolant temps (thanks, Florida heat and humidity!). While not every vehicle would need a hard-part upgrade like this, every vehicle can benefit from a cooling additive like Royal Purple’s Purple Ice. This is a synthetic radiator coolant additive that reduces engine heat by reducing the surface tension of the radiator fluid, improving heat transfer. Purple Ice also optimizes coolant flow by helping to prevent formation of scale deposits in the radiator, and it lubricates the water pump seals too.

To get to the bottom of that fancy wording, we tested Purple Ice on two vehicles with real-time scan tools: our G-body before the SPALs, and an LS1-powered 2002 F-body. We tested these cars in three situations: warmed up and idling for three minutes, at 55 miles an hour for 10 minutes, and in stop-and-go, 35-mph traffic for 10 minutes.

Needless to say, Purple Ice made a real difference in coolant temperatures. Besides the high, 210-degree G-body idle reading (with 160-degree thermostat, no less) that made it pretty clear that a fan upgrade was needed, Purple Ice consistently dropped both cars’ coolant temps. With summer just around the corner, this is the best few bucks you can spend on your hot cruiser!

1987 G-BODY   
Purple Ice210190175
2002 F-BODY   
Purple Ice213198203

Tests performed in 85 to 90-degree temps, with 60-82% humidity. Scan tools: FAST XFI ECU with laptop control, and FAST handheld tuner for LS1.







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