Pontiac Cooling System Upgrade - Cool Winds
With winter starting to rear its ugly head in the colder regions of the country, the steamy days of the past summer may seem a distant memory, but not for those among you who suffered from cooling system maladies in your favorite classic Pontiac. Though it may seem counterintuitive to discuss engine cooling at this time of year, the truth of the matter is that most of you finally have the time to do something about your poor-performing cooling system since your Pontiac won't be showing or cruising for a while.
In Part I, we introduced you to a '66 Tempest owned by Floyd Hand of Dallas, Texas. It is a stellar performer and routinely runs mid 11-second quarter-mile e.t.'s, utilizing a 0.030 over 455 and Jim Hand-ported iron No. 7K3 cylinder heads. Its stock-type cooling system was ready for an upgrade, so we detailed the installation of its new components.
The decision to employ an aluminum Performance Rod and Custom (PRC) radiator, SPAL 16-inch electric fan and Meziere electric water pump and the required Butler Performance Alternator Relocation Kit was more geared toward improved dragstrip cooling, with street performance a close second. The Meziere electric pump-unlike the stock mechanical pump-can be run in the pits with the car shut off to cool the engine much more quickly between rounds. The fact that the pump is stated to work on the street as well was an added bonus that would allow the weekend racer, who likes to drive to the track, to have his cooling-system cake and eat it too, so to speak. Though we had little doubt that the modifications would show improvement at the track, the question was how would the electric pump and the remaining components fare around town and on the highway?
To that end, in Part II we will test the effectiveness of the upgraded cooling system in many situations and endeavor to maximize its efficiency.
The Testing Parameters
Testing of the '66 Tempest was performed utilizing a Raytek AutoPro Infrared thermometer and an aftermarket in-car mechanical coolant temperature gauge mounted in the intake manifold crossover. The infrared thermometer was pointed at the "pad" located above the spark plug on cylinder No. 1 (driver side front cylinder) and cylinder No. 6 (passenger side, third cylinder from front). After determining that the mechanical gauge matched the readings when the SPAL relay turned on and off (185 and 165 degrees respectively), the SPAL sensor was moved to the No. 6 cylinder.
Four different conditions were tested. The first was "low-speed" cruising, which amounted to driving the car at speeds that were between 25 and 40 mph for two miles. The second condition was "high-speed" and was for all intents and purposes a hard quarter-mile pass, immediately following the recording of low-speed readings. The third series of tests was "highway," which consisted of driving the car between 55 and 68 mph for 10 miles on a rural interstate. The fourth series of tests was "extended highway"-a 50-mile round trip on an interstate highway driving between 65 and 70 mph. After completing each test, the Pontiac was pulled to the side of the road and left idling. A reading was taken from the in-car gauge and then the hood was popped open to take infrared thermometer readings.
The Baseline
The '66 utilized an OEM-style four-core brass and copper radiator with a shroud from a GTO. Equipped with a stock-type iron water pump, a seven-blade factory clutch fan and a 160-degree Stant SuperStat thermostat, the Pontiac didn't overheat-but it did routinely see over 200-degree coolant temps after being driven hard on the street, or at the end of the quarter-mile. When driven on the highway, the coolant temps steadily climbed to 210 degrees.
The Upgrade
The new cooling system consists of a custom-built PRC aluminum two-row radiator (retail $410) and a custom shroud ($100) that houses a SPAL 16-inch electric puller fan (PN 30102047, retail $157.95), a 185-degree thermo switch and a wiring harness (PN 185FH, retail $55.95). Coolant transfer duties fall to a Meziere heavy-duty electric water pump (PN WP103BHD, retail $315.00) that required a Butler Performance Alternator Relocation Kit (PN TRP-ALT2, retail $85) mounted on the passenger side of the engine compartment.
Surprisingly, after upgrading the cooling system, its performance was surprisingly slightly inferior to that of the OEM-style system (see Test Results). This didn't make sense, especially considering that the OEM-style system was getting long in the tooth and the quality of the new components are top-notch. Where the system did excel was cool down between passes. It took less than two minutes with the car shut down and running the electric fan and water pump to reduce the coolant temperature to 160 degrees.
Since the Pontiac would serve double-duty, however, we needed a system that would be superior to the OEM style at the dragstrip and equally capable of hitting the highway for extended periods of time. Two critical factors beyond the design of the replacement parts determine how well a cooling system will operate: airflow and coolant flow through the radiator. An investigation ensued to isolate and determine where cooling improvements could be made. Details of what worked and what didn't will follow. However, the results of our efforts are listed below so you can see how well the system ultimately performed.
The Final Setup
The final cooling system configuration consists of the same components listed in the upgrade section, but instead of using the PRC custom aluminum shroud, the electric fan was mounted against the radiator using equipment supplied by SPAL that included fan brackets (PN 30130011, retail $1.49 each), a strap kit (PN 30130071, retail $2.95 each) and a fan gasket (VA18, retail $7.95). An Ames Performance A/C seal kit was also installed.
The end result was a 20-degree drop in temperature during the 10-mile highway test. Even when driving the Tempest for 50 miles in 92-degree heat, the temperature never rose above 190 degrees. High-speed tests revealed a 7-degree improvement. The low-speed testing results changed little from baseline, but that was because the system we replaced already worked fine at low speeds, so no substantial improvement was expected in that area.
Cooling System Investigation
Now that you see the results of our tweaking the system, it's time to learn how we got there.
Coolant Flow
Coolant that flows too fast through the system will not allow sufficient time for cooling by the air that passes through the radiator core. Conversely, coolant that flows too slowly spends more time in the engine block where more heat transfers through the water jackets into it.
To test whether the water pump was moving coolant too quickly through the radiator, the owner pulled out a vintage Moroso water outlet restrictor kit that consists of three restrictors, which range in size from 5/8-inch through 1 inch. The 5/8-inch restrictor will cut coolant flow approximately by half, while at the other end of the spectrum, the 1-inch restrictor is almost identically sized to the diameter of the thermostat. Rather than test all three sizes, just the largest and smallest sizes were utilized. To determine if the thermostat itself was causing a restriction, it was removed for the final coolant flow test.
5/8-inch Restrictor-After installing the 5/8-inch restrictor, it was apparent that restricting the water pump flow had a detrimental effect on overall cooling. Temperatures were elevated in low-speed testing, averaging 193 degrees. At the conclusion of high-speed testing, the gauge read 216.5 degrees and highway testing resulted in 230 degrees. The Tempest was within seconds of boiling over had it not been shut down and allowed to cool on the side of the road.
1-inch Restrictor-Once sufficiently cool, the Pontiac limped home and the restrictor was changed out to the smallest one (1 inch). Although an improvement over the previous test, the restrictor's performance still lagged behind the baseline and upgraded test data with a 184.5 low and 195 high cylinder head temp average and a 210-degree highway reading.
No Thermostat-The final test involved removing the thermostat entirely. Once again, the performance improved, but the overall results still weren't as good as when we began. The cylinder head average temp checked in at 176 degrees and 191.5 degrees, low and high respectively. Highway temp was 210 degrees.
According to Don Meziere, owner of Meziere Enterprises, "The Meziere water pump supports engines up to around 550 horsepower and has a free-flow rating of 40 gallons per minute. When measured in actual flow rate on an engine, it flows between 16-18 gpm, almost identical to what the stock-type pump does at higher rpm with far superior low-rpm flow ratings."
Having proved that restricting the water pump flow was detrimental to cooling system performance and the thermostat itself wasn't a restriction, it was time to focus our efforts on airflow through the radiator.
Air Flow
The primary function of an engine's cooling fan is to draw a sufficient volume of air though the radiator at idle or low speeds to maintain a safe coolant temperature. Once the vehicle reaches approximately 50 mph, a cooling fan provides little benefit, as the primary cooling occurs via air that flows through the front grille or is directed under the front end and into the radiator.
In order to maximize the volume of air that flows through the radiator, a call was placed to Ames Performance to procure an air conditioning seal kit. Though the Tempest was originally AC-equipped, the system and all of the seals had been removed by a previous owner. (In the baseline configuration, hardware store plumbing insulation was used to fill the gaps on the sides and top of the radiator.)
Initially, only the sides and top of the seal kit were installed to "replicate" the amount of sealing from the baseline OEM-style radiator. After completing that test, the front bumper was removed to facilitate installation of the lower seal kit components and the tests were run again. At the conclusion of testing, there were significant increases in cooling system performance.
Upper Seal Kit-Though the cylinder head temp averages were 181 degrees low- and 188.5 degrees high-speed, the highway temp dropped 5 degrees, to 205.
Upper and Lower Seal Kit-With the lower seal kit installed, more good news followed. The cylinder head temperature averages for low-speed and high-speed dropped to 169 degrees and 170.5 degrees, respectively. High-way temperature stayed at 205 degrees. (It is important to note, however, that the ambient temperature had dropped to 90 degrees for both seal tests since the baseline and upgrade tests were performed.)
Shroud Flaps
Since additional airflow proved beneficial to overall performance, Shawn Kenney of PRC and Heath Langenfeld of SPAL suggested that in a small percentage of applications the fan shroud could prove to be a restriction. According to Langenfeld, "Moving from a factory fan shroud opening of 21 inches down to 16 inches restricts the volume of air flowing through the radiator. The reduced diameter of the hole has a funnel effect and on big-cubic-inch applications, it is often necessary to make alterations to the shroud. To cure the problem, we recommend installing rubber flaps onto the aluminum shroud. They will remain closed at slow speed and then open up at high speed to allow more air to flow through the shroud."
After testing the rubber flaps, the performance on the 10-mile highway test improved, allowing the car to run right at 200 degrees. Compared to the earlier final A/C seal kit test, the low- and high-speed cylinder head averages of 176 degrees and 185.5 degrees were up a bit but so, too, was the ambient temperature, at 92 degrees.
Having proved that increased airflow was beneficial to overall highway performance, SPAL suggested that the shroud be removed and the fan mounted to the radiator core. As you already know, that final setup showed the best performance (see Test Results).
After examining and testing both coolant flow and airflow through the radiator, it was determined that any reduction in coolant flow brought with it increased coolant temps.
Airflow testing resulted in the addition of two key items that allowed significant improvements in cooling. The Ames Performance air conditioning seal kit allowed more air to be directed through the radiator and, although the PRC custom shroud was very attractive, it limited the volume of air passing through the radiator so the Tempest ultimately ran cooler on the highway without it. Fortunately, though low-speed performance without a shroud should have decreased, it didn't, showing just how strong the SPAL fan is in drawing air through the radiator. Performance at high-speed and on the highway showed the most dramatic improvements with a 20-degree reduction in coolant temperature.
In addition to significantly improving overall cooling system performance, we dispelled the rumor that electric water pumps are only appropriate for strip cars that see limited real-world usage. Anytime you can cruise the interstate for 50 miles at the posted speed limit and never exceed 190-degree coolant temps, you can be confident that you can hop in your Pontiac and drive to work or load up and travel a few states away to hit a national Pontiac event. With a rating of over 2,500 hours of continuous use, the water pump should last well over 75,000 miles and provide flexibility at the dragstrip to always be at or below your thermostat rating even if you are required to hot-lap your car for the next round of eliminations.
If your ride is in need of a cooling system upgrade, consider checking in with these vendors. In addition to quality parts at reasonable prices, they all provided timely and accurate technical support to make sure that the system was optimized.
Although the snow may be swirling and a football game is about to start, there's no better time than the present to prepare your Pontiac for next summer.
Test ResultsLow SpeedInfoBaselineUpgradeFinal SetupAmbient Temp Degrees95.093.092.1Humidity (Percent) Pressure29.829.829.9No. 1 Cylinder168.0173.0170.0No. 6 Cylinder178.0176.0176.0Cylinder Head Average173.0174.5173.0High SpeedInfoBaselineUpgradeFinal SetupAmbient Temp Degrees95.094.092.1Humidity (Percent) Pressure29.829.929.9No. 1 Cylinder184.0186.0176.0No. 6 Cylinder186.0191.0180.0Cylinder Head Average185.0188.5178.0Highway10 Miles 210.0210.0190.050 Miles----190.0
Recommended Tools
Standard socket set
Standard wrenches
Allen wrenches
Cut-off wheel or grinding wheel
Drill and drill bits
Recommended Parts and Supplies
(20) 1/4 x 3/4-inch carriage bolts
(20) 1/4-inch lock nuts
Electrical strapping

Photo Gallery: Pontiac Cooling System Upgrade - High Performance Pontiac Magazine

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