Ames' A/C seal kit for '66-'67 Tempests and GTOs (PN P168, Retail $32) consists of 13 pieces of die-stamped masticated rubber. The seals attach across the top, down the sides, and across the core support to force the maximum amount of air through the radiator.
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.
Ames supplied a complete fastener kit (PN P168DK, retail $35.00) that included six unique push-in top seal clips, along with the other clips to allow installation of the seal kit. | 
SPAL provided a total of six rubber flaps to install PRC's fan shroud to further improve highway cooling. They were designed for their dual 11-inch fans (PN 30130012, retail $1.25). Each flap measures 3 1/4 inches long by 2 inches wide. After removing the shroud, a cutoff wheel is used to cut 2 3/4 x 1 3/4-inch holes in it. | 
After cutting the six holes, a No. 35 drill bit (0.110-inch in diameter) is used to drill three small holes through which the tabs of the rubber flap will protrude to affix the flap. |
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.