The Stovebolt Site Forums The Shop Area Engine Shop Rear Engine Water Drain NPT Size?

I am trying to figure out without draining the water out of my engine what the rear drain on our engines is sized. 1/4 NPT or 3/8 NPT. Depending on how I hold my head while staring at the outside of it, I could go either way. Anyone know for sure. I think they are the same for the 216/235/261 engines.