Better yet replace the valve with dummy (flapper removed) or a spacer. The counter weight goes down as it opens. It should operate freely by hand and open during acceleration and cruise.
The exact specifications can be found in the shop manual available for each year from CTCI. The 1957 model must be set in three places, initial, centrifugal and vacuum for acceleration. The initial advance of 3-6 degrees and the vacuum advance for acceleration and cruise.
Install a full radiator fan shroud (including lower section).The edge of the fan should be out of the shroud approximately ¼”. Install a six blade fixed (nonflexible) fan.Head gaskets properly installed (square corner tab should be visible at the top front of the engine block) and are not leaking.Other items that contribute to a cooler running engine are as follows. This combination has proven to be very effective without ill effect.
In addition a thermostat with a larger opening can also be used. The extended impeller was developed by CASCO and is available from them and maybe other dealers. After the rust is removed, a high volume water pump with an extended impeller can be installed. This can be done with the engine in the car, but best done with the engine removed. The rust must be removed by breaking it loose and flushing it through the core plug holes. This problem can be overcome first by cleaning the block. The above conditions cause overheating especially during city driving or parades. This lesser volume of coolant coupled with infrequent radiator flushes and coolant changes created an accumulation of solid rust around the rear cylinders of the block. The results were a lesser volume of coolant being pumped through the engine. When this spacer was installed the water pump impeller did not fill the extra one inch gap created by the water pump spacer. When the same engine was used in a Thunderbird it was necessary to install a 1&1/8″ spacer between the water pump and mounting cavity to accommodate belt alignments. This combination worked fine in the passenger cars and trucks. The water pump impeller was approximately ½” thick. The cavity for the water pump impeller was approximately 5/8″ deep. The timing cover for both the passenger car and Thunderbird were similar in design, both were built to accommodate the same water pump. The water pump for the Thunderbirds was the same as used on passenger cars and trucks. The T’Bird engines were the same engines used in thousands of Ford passenger cars and trucks, but the passenger cars and trucks did not have the same tendency to overheat.
Also, there is a basic design flaw in the water pump system.
The small tight engine compartment did not allow for free air flow to carry out the hot air transferred from the radiator. The primary reason for higher than normal operating temperature under these conditions was due to the design of the engine compartment.
Even when new, under certain driving conditions (parades & city driving) when coupled with excessive ambient temperature, the Thunderbirds were prone to run toward the hot side of normal.
When it comes to the7 Thunderbirds, this subject more than likely, has been discussed and written about more than any other.