Broken Camshaft

I bought an 88 300zx turbo that was listed as having a rod knock. I determined that the noise was coming from the passenger side camshaft, so I pulled the timing cover to inspect it. The belt was fine and I couldn't move the cam by hand, so I started the engine and revved it up a bit, and the cam simply snapped in half inside the head. I'm not concerned one bit about the engine, but I'd like to know what may have caused this to happen. I was told that it was overheated and that caused the knocking. It was parked, sold, and then sold to me, so I can't really get the full story.

Any ideas?

Lack of lubrication causing the cam to seize in the support saddles would be the usual reason, so a rod knock, hence lo oil pressure could be the source of the problem.

Different engine, but I had a camshaft brake in half in a GM 3100 V6 engine. The engine had been damaged from running with coolant in the oil, and after replacing the head gaskets and intake manifold gaskets, lubrication to the upper structure was never good again. It finally spun a cam bearing. The cam broke in half, and the block was wasted.

Different engine, but I had a camshaft brake in half in a GM 3100 V6 engine. The engine had been damaged from running with coolant in the oil, and after replacing the head gaskets and intake manifold gaskets, lubrication to the upper structure was never good again. It finally spun a cam bearing. The cam broke in half, and the block was wasted.

I seem to recall this was a common failure for some 3100 V6 engines.

Yep. Sure was, mainly because coolant in the oil was such a common failure because of leaking intake manifold gaskets.