1987 Camero 305, broken part ?

It's located on the passenger side of the engine under the exhaust manifold

Picture is poor but from where you described to was that should be the knock sensor.

Yes, I vote for the knock sensor. Remove it and if coolant comes out, that's what it is. The knock sensor is also the cooling system drain for the head on these engines. Hope that helps! Jim

You're welcome Bob.