I believe the Cummins part number is 3902606 which is superceeded by 3922073 but they don't list the size and i am trying to replace a leaky freeze plug on an engine up at our ranch. it is the expansion plug right by the valve cover and the injector in the head.

Its actually on a 4bt cpl # 857 from 1989 but it uses the same expansion plugs as my old dodge 12 valve.

I went into the local cummins supplier and they said 1-2 weeks to get in the correct freeze plug. Napa didnt have anything listed intheir system and I dont have a 12v or 4bt available to me to measure before i head back up to the ranch. so it's one of those rock and hard spot situations where i need to ask others for that super simple answer which is

What standard size is that darned freeze plug in the top of the head

thank you i could definately use the help today if at all possible since i am planning to go up and do the install on friday