CTCI Authenticity Chairman
Because of its large opening the NAPA # 6 has been a very popular thermostat for our Thunderbirds.
An alert tech article reader, Ted Woods, Palm City, FL, has brought to my attention a potential problem with this particular thermostat when used in 1957 models.
This thermostat functions fine with the 1955/56 intake manifolds, as well as the 1957 E models. The problem occurs on the 1957 intake manifolds because the heater control valve threaded port was moved forward to accommodate the larger carburetor.
As the thermostat opens, it extends and contacts the extension pick up tube for the vacuum operated heater control valve P/N 18495 . This problem can be eliminated by removing the extension tube on the bottom of the heater control valve.
The extension is threaded into the valve and can be removed by turning it counter clockwise. Once removed the NAPA # 6 thermostat can open fully. Removal of the extension does not effect the operation of the heater control valve.