i wanna say it's 12x1.25 , it's either 10mm or 12mm and i wanna say it's 12mm, i did one on a GReddy intake manifold the other day, but now that u ask me i'm unsure of myself lol
when you buy the autometer coolant gauge, it comes with the sending unit and some threaded "bushings" to bump up the size, if u take the one for the next size up and grind the threads on it smooth, then use the12x1.25 die to make the new threads. that works. use thread teflon goo, not teflon tape, goo will let your sensor get a good ground so it can give the guage the correct reading since the sending unit gets voltage and the waxy element inside provides less resistance the hotter the sensor gets.
gl man,
Dave @ Lethal Injection Motorsports
www.LethalMotorsports.com