This seems like an excellent tip. Wonder why they don't make them that way from the factory?
The OEM design didn't have a hole in them, as it really isn't necessary. I've seen OEM thermostat that did have them, usually on vehicles that have the thermostat in a position lower than the head, or it is is positioned vertically rather than horizontally.
I've personally never had a problem filling a system with an undrilled thermostat.
I experienced air in the cooling system in the 355 SBC in my Model A Hot Rod a few years back.
Basically in the spring the first time I drove the car, after it was stored through the winter, it over heated. That simple little hole in the thermostat would have saved me a bunch of heartache and a bit of wrenching.
From my perspective the hole doesn’t hurt anything, but has the possibility of preventing a problem, so why not?
