My truck (87 F250) would smoke white smoke when it was started cold, but cleared up when it warmed up so I was going to replace the injector O-rings. On the way to get back to where I was going to work, it started to billow white smoke (enough to smoke out the entire street behind me), clicking, and shaking so I pulled in to a parking lot. I got a tow and I pulled the injectors (can post a picture if needed) and all of the injector cups have some carbon built up, but two of them had some greenish gunk with some grit. I didn’t know what to think because as far as I can tell there’s no coolant in the oil (no gray) and I know that I didn’t lose any coolant because I had just checked it the day before and it was at the same level. Could this be an injector problem or am I looking at head gasket(s)?