I have a 1993 z28. Just took the intake off the engine after discovering a mixture of coolant and oil in the throttle body. There seems to be more of both in the breather hose that runs to the passenger side valve cover. However when I drained the oil there appeared to be no coolant in it. Just oil (which probably needs to be changed anyway). Correct me if I’m wrong but this would lead me to believe that it’s likely not my head gasket that’s the issue. I would assume the oil in the pcv breather would indicate that’s the sole reason for oil in my intake. But I don’t understand where coolant fits into this. The previous owner did the coolant mod that bypasses the throttle body, so there should be no coolant running through my intake or throttle body. Below are some pictures of what it looks like. Also if anything I’ve said makes no sense I apologize I’m somewhat new to this. Never dealt with pcv or coolant/oil issues til now.

 

Most likely condensation from temperature variation. especially prominent during cooler ambient temperatures. you can confirm by taking the spark plugs out to see if any of them have been steam cleaned, check coolant level, and do a coolant pressure test (while the plugs are out).

 

Agree with the above... Highly likely just condensation and oil mist.

One thing that may help is adding an oil separator in-line with the PCV.