I bought a set of TFS heads used from a board member here, and there was a brass thread adapter screwed into the coolant temperature sending unit hole since the tapped hole in the head is larger than the sending unit thread. The thread on the sending unit is 3/8-18. Does anyone know the size of the hole in the head? 1/2"? I need to buy a new adapter. I could obviously pull it out and go size it myself, but I'm at work all day today and I'd like to stop by the store on the way home and pick it up. Thanks.

 

you can get an adapter at advanced auto parts. maybe someone knows the sizes by heart and will post them. if not just take a head and sensor with ya, to the store

 

Did some research, the answer is 1/2-18.