TESTING A RADIATOR AND SPAL FAN FROM U.S. RADIATOR
Testing a radiator and SPAL fan from U.S. Radiator
For the last four decades, auto manufacturers have embraced the use of electric fans. Electric fans first appeared on lowpowered, emissions-laden front-wheeldrive cars that were in dire need of reduced parasitic power losses whenever possible. While reducing parasitic loads on the engine at cruising speeds, these electric fans still provided excellent lowrpm cooling when idling or at low vehicle speeds. Our original intent was a dyno test comparison of the factory-fixed fourblade fan and an electric fan setup on our ’67 six-cylinder Dart GT, but as luck would have it, the 51-year-old radiator sprang a leak just as we completed our baseline dyno runs, so we were on the search for a radiator and electric fan setup. We contacted Don Armstrong of U.S. Radiator, and he set us up with a radiator, SPAL fan, and custom shroud for our Dart. U.S. Radiator has been in business for more than 40 years, and the staff has plenty of cooling system experience with all types of vehicles and manufacturers.
The test vehicle was Pennsylvania College of Technology’s (PCT) “dyno” Dart. The original 22K-mile Dart was donated to the college in 2012 and has become a test mule for various bolt-on components in the college’s dyno classes. The Dart has a rebuilt Slant Six (machined and assembled in the college’s machine shop with an increased compression ratio of 9.37:1, a result of a combination of decking the block and milling the head. To ignite the air/fuel, an electronic ignition has been installed to replace the single-point ignition. A 2.25-inch Accurate Exhaust Products full exhaust handles removing the spent hydrocarbons. The rest of the drivetrain remains as the factory installed it in late 1966.
To establish our baseline, we tested the performance of the radiator and the factory four-blade fixed fan. The Dart was run on the PCT Mustang dyno in an rpm range of 2,200 to 4,000 rpm. The engine could’ve been run a few hundred rpm higher than 4,000 rpm, but the horsepower peak was already trending downward at four grand, so there was no need to beat the Slant Six. We made a series of three baseline runs within 1 percent of each other, and the 225 spun the rollers to a peak of 149 lb-ft of torque at 3,100 rpm and 95 hp at 3,800 rpm. Upon completion of our third run of the series, we noticed a small pool of coolant on the shop floor under the Dart. We knew what that meant; we were now in search of a new radiator to complete the testing. We were just thankful to complete our baseline testing.
U.S. Radiator supplied a high-efficiency radiator (20 percent more heat transfer points over original equipment), and the use of a 22-inch (width) replacement radiator rather than the 19-inch factory radiator was suggested. The 22-inch radiator would fit in the factory radiator support opening without any modifications, so we agreed to the bigger radiator for our testing. The fan selected was a 16-inch SPAL puller fan that would provide more than enough airflow across the radiator. We made all the measurements we could to determine the fan fitment, and U.S. Radiator took our measurements and fabricated a fan shroud with a fan opening to the maximum right (passenger side) of the radiator to clear the factory water pump pulley.
When the radiator arrived, the radiator, fan, and shroud were completely assembled and ready to drop in to the engine bay. Even with all our measurements, the fit between the fan and the water pump pulley was tight. The fan depth caused some concern. We pushed the radiator to the right (passenger) side as far as the bracket bolt slots would allow to provide enough clearance between the water pump pulley and the SPAL fan motor. Once we had the clearance we desired, we loosened the driver-side engine mount and jacked up the engine to see how much engine movement could occur before any contact between the pump pulley and the fan motor occurred. We still had clearance at a point well beyond any engine mount deflection under acceleration.
The SPAL fan comes with an installation kit that requires a temp sending unit to be installed in the cooling system, near the engine’s thermostat. This would’ve been straightforward on a V-8 engine,
because the intake manifold has one (or more) provisions for the temp sending unit to be inserted, but a Slant Six engine doesn’t provide such access. U.S. Radiator could’ve put a bung in the upper radiator tank for us (if we had asked), but we ended up modifying a piece of 1½-inch outside diameter (od) exhaust pipe, which we drilled, tapped, and then installed the sending unit bung. We used cold weld (two-part epoxy) to affix and seal the bung to the pipe. Once cured, the temp sending unit was threaded into the bung. We
installed the sending unit housing into the upper hose with the temp sending unit pointing downward. A pair of hose clamps secured the housing into the hose.
With the radiator assembly and temp sending unit installed, we had to wire the fan. The SPAL installation kit provided a 30-amp Bosch relay and harness to wire the fan. We mounted the relay next to the radiator and the battery at the driver-side corner of the engine bay. Following the instructions, we supplied a fused 12-volt source to pin 30 (power side) of the relay, and a switched (ignition) 12-volt source to pin 86 (control side) of the relay. Pin 85 (control side) was run to the temp sending
unit that we had installed into the upper radiator hose. We ran pin 87 (power side) of the relay to the fan 12-volt wire and grounded the other wire from the fan. After completing the wiring, we added the coolant to the radiator and checked the upper hose several times for any leaks.
The ’67 factory cooling system didn’t have an overflow tank, which meant there was no reservoir for the overflow coolant from the radiator. In this system, the upper tank is designed to be the expansion tank. The coolant is filled to the top of the core not the top of the tank. The tank acts as the overflow area when the engine warms. The problem with this design is coolant loss onto the ground and debris entering the radiator leading to contamination and reduced cooling system efficiency. We elected to install a generic overflow tank to the Dart. We could now completely fill the radiator’s top tank, and the overflow tank could be filled to the fill cold line. When the engine was run, the coolant would push out of the radiator into the overflow tank, and when the engine cooled the coolant would be drawn (pushed back into) the radiator. This design would end any coolant leakage onto the ground and limit contaminants from entering the cooling system. We installed our overflow
tank inside the passenger-side fenderwell. For now, we zip-tied the overflow tank to the bumper bracket and will determine a permanent position for it in the future.
With the radiator’s top tank filled with coolant, we topped off the overflow tank and warmed up the Slant Six. We constantly checked the temp sending unit housing in the upper hose for leaks and found none. The engine’s temperature continued to rise, and just about the time we thought something might be wrong with the fan’s wiring, the fan spun to life. The fan was designed to turn on at 180 degrees F and turn off at 165 degrees F. In conjunction with the 160 degrees F engine thermostat, the fan operated properly, cycling several times while the slant idled. We used an anemometer to measure the electric fan’s ability to pull air across the radiator and compared it to the four-blade fan measurements. The electric fan pulled
a constant 3.5 mph of air across the radiator regardless of the area of the radiator tested. The factory four-blade fan could match the 3.5 mph speed of the electric fan in the center of the radiator, but the speed fell off greatly as the anemometer was moved to the edges of the radiator.
Back on the dyno, the Slant Six was run through the same parameters as the baseline runs. We made each run with the electric fan in operation to compare the performance difference between the fixed fan and the electric fan. After the series of runs, the electric fan showed a mild increase in torque and horsepower, and most of the improvement was in the higher rpm of the run. The peak torque was up to 151 lb-ft at 3,100 rpm, and the peak horsepower rose to 99 hp at 3,900 rpm. The torque climbed 2 lb-ft, and the horsepower increased by 4 hp.
Was the electric fan worth the effort? Well, 4 hp at the wheels is an increase. For the sake of simplicity, Armstrong suggested we add a U.S. Radiator custom shroud, radiator, and flex fan, while foregoing the electric fan idea for the slant. We — now — agree, as we had concerns with the electric fan (a 7-amp additional draw with an 11-amp ramp up draw) taxing our 35-amp alternator and worse adding additional loads to the 51-year-old wiring harness. If an electric fan is in your future, consider upgrading your entire charging system to meet the needs of the new electrical requirement (For information about upgrading your charging system, review “Electric Avenue Charging System Upgrade with a Tuff Stuff Alternator” from our July 2018 issue.)
U.S. Radiator provided us with everything we needed to upgrade the cooling system of our Dart. Would this installation have been easier and more suitable on a modified V-8? Yes, but U.S. Radiator delivered a perfect package for our Slant Six Dart. In the case of the Slant Six, we shouldn’t have been so determined to have the electric fan and listened to Armstrong’s suggestion about the flex fan option, which would’ve saved us time (temp sending unit housing mods and radiator fitment). It wouldn’t have altered our charging system requirements, and the performance gains would have most likely, in the case of the Slant Six, been similar. If you need a radiator, shroud, fan, or even guidance as to what to do with your cooling system, contact the representatives at U.S. Radiator. They’ll provide you with 40-plus years of experience and knowledge, and point you in the right direction. It’s up to you to heed their advice.
The radiators are similar in design; however, the U.S. Radiator is a high-efficiency radiator (20 percent more heat transfer points over original equipment) that’ll meet the cooling needs of the rebuilt 225 Slant Six. Additionally, the radiator from U.S. Radiator is all-new, so it’s void of 51 years of contamination and debris.
The Dart was run on the Pennsylvania College of Technology’s Mustang dyno in an rpm range of 2,200 to 4,000 rpm. The 225 Slant Six with the fixed factory four-blade fan and 19-inch radiator established a baseline of 149 lb-ft of torque at 3,100 rpm and 95 hp at 3,800 rpm. At the completion of the third run of the baseline runs, coolant was noticed on the floor under the radiator support.
The 51-year-old radiator looks dry at the top tank, but just above the bottom tank, the core had some previous damage that finally split open and began leaking during the testing. The Dart came from the factory with a fixed fan and no shroud.
The factory 19-inch radiator (left) provided 51 years of service, but during our latest testing it finally started leaking. The solution was a radiator, custom shroud, and SPAL electric fan from U.S. Radiator. The radiator is a 22-inch design, which fits into the factory radiator support opening at the front of the ’67 Dart GT test car.
The upper and lower radiator hoses were removed, and the transmission lines were disconnected from the cooler in the bottom tank. The two upper radiator retaining bolts were removed, and the two lower bolts were loosened but not removed. With a little tilting of the radiator toward the fan, the radiator was pulled out of the Dart’s engine bay.
With the radiator out of the way, the fixed fan bolts were easily removed. The four bolts, the fan, and a fan spacer were removed. We left the water pump pulley in place, so the pulley and the water pump flange remained lined up for the installation of new water pump pulley bolts.
Coolant leaked onto the lower radiator support, down the support strut to the K-frame and onto the transmission line. The radiator could’ve been re-cored, but U.S. Radiator supplied a better-thanfactory new radiator for our testing.
We found suitable (shorter) bolts to attach the water pump pulley to the water pump flange. We used lock washers on the bolts to minimize any concerns of the bolts backing off. When selecting new bolts, check the back side of the water pump flange to make sure the bolts aren’t too long, resulting in interference with the water pump casting.
Both transmission line flare fittings were removed from the 19-inch radiator and transferred to the new 22-inch radiator. If new fittings had been required, they’re a male connector 1/8 NPT on the cooler end and AN-05 (5/16) flare on the transmission line end (PN Edelmann 148520, Everco 48D, or Weatherhead 48x5).
For the radiator drain, a new plug was picked up at a local auto parts store. The factory petcock in the 19-inch radiator was physically damaged and too corroded to transfer to the new radiator.
With the radiator drain plug and transmission cooler fittings installed into the lower tank, the radiator was dropped onto the lower radiator bolts that had been left in the radiator support. The radiator was pushed to the right (passenger side) as far as the radiator bracket slots would allow, so maximum clearance between the SPAL fan motor and the water pump pulley could be attained. With the radiator in place, the four radiator bolts were tightened.
While at the auto parts store, we picked up a bung (left) and shortened it to the length we desired. The SPAL temp sending unit threaded into the bung. We ensured the sending unit would be in the flow of coolant at all times to provide an accurate temperature measurement. U.S. Radiator could’ve provided a bung in the upper tank if we had asked, but our modification did the job.
A piece of 1½-inch outside diameter (od) exhaust pipe was used for a place to install the temp sending unit bung. The pipe was drilled and tapped, and the bung was installed. This pipe would be shortened and fitted into the upper radiator hose.
The bung was threaded into the pipe and then glued into place with a twopart cold weld epoxy. The pipe was shortened to the desired length, and when the epoxy dried, the assembly was sanded and painted black.
The upper radiator hose was cut to accommodate the new temperature sending unit assembly. A pair of hose clamps held the exhaust pipe in place. The temp sending unit was threaded into the bung.
The Bosch relay was mounted on the upper radiator bracket bolt on the driver-side upper radiator support. The wiring harness uses weather-pack (blue) seals to reduce any water or debris from contaminating the circuits. A fused 12-volt source was supplied to the yellow wire, and a switched (ignition) 12-volt source was applied to the orange wire of the relay. The gray wire was run to the temp sending unit installed into the upper radiator hose, and the red wire was the 12-volt wire to the motor.
The SPAL electric fan wiring harness included a 30-amp Bosch relay, several fuses and wire ends, shrink-wrap butt connector, fan connector harness, inline fuse holder, and wiring instructions. We wired the fan as outlined in the instructions.
The heavy-gauge red wire was connected to the fan connector harness’ red wire. The provided shrink-wrap butt connector was used. The shrink wrap protects the wires from contamination. The gray wire was run to the temp sending unit, and the black wire (under left hand) was run from the fan to a chassis ground. When the wiring installation was complete, the wires were all tucked behind the factory harness on the radiator support.