Technical Thread size for ‘29 Model A temp gauge in radiator??

Does anyone know what thread size this is?
I’m missing the Threaded temp Gauge piece in my 29 Ford and need to plug the hole.

thanks!

dean

 

What's the cap from? I can't remember seeing one of those on an "A" unless it was an aftermarket accessory.

Sent from my SM-G892A using Tapatalk

 

That's not a Model A radiator cap. Any after market Moto-Meter should fit into the hole in your cap. Bratton's has them PN 25610. They also have the correct cap for your radiator. If you don't want to use a Moto-Meter, I would get a brass carriage bolt with a rounded off top to fill the hole.

 

thanks for the help!