All thermostats have some means of air bleed built in. If you hold them up to the light, you can see the seat or the disc has a wavy edge, or a notch cut in it to provide air bleed/minimum flow. The only exceptions are the kinds that have a separate disc to open/close a bypass.
1952 F-1 Flat V8 3-on-the-tree MSD, Rochester 2G, Red's Headers
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