In addition to the six flaps supplied by SPAL, the owner crafted two additional ones out of heavy rubber and mounted them with sheetmetal screws. Once complete, a total of eight flaps were installed and the shroud and electric fan were mounted so additional tests could be run.
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.)
Once it was decided to remove the shroud entirely, SPAL supplied a set of four fan-mounting brackets (PN 30130011, retail $3.95 each) along with a 16-inch fan gasket (PN 30130074, retail $8.93). Each mounting bracket snaps into a corner of the fan and swings out so that it can be attached to the core support. The thick rubber fan gasket slips over the edge of the fan and provides cushioning to ensure that the unit doesn't rub a hole in the soft aluminum radiator core.
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 [95 degrees] and upgrade [94 degrees] 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).