I was driving home the other day and I missed a shift and over revved the alfa. it started making an awful banging noise. At first I thought the clutch was starting to come apart because it shifted really hard and pushing in the clutch seemed to make the throw out bearing squeal. Upon inspection the clutch seemed fine. I took the cam cover off and noticed the timing chain was very loose. I adjusted the tensioner, checked the cam timing and the valve clearance. I put it all back together. The banging noise is not as pronounced now, and only at idle and right above, but it is still there. I checked timing again and when I reached down to try to turn over the engine, I noticed the crank pulley rotated on the crank about 1/4 turn without the crank turning. I pulled out the radiator to get a better look, with frars of the crank nose being broken. I see that the pulley spins on the crank, but the TDC mark on the crank nose is in alignment with TDC measured with a dial gauge on the piston. I have not puuled the pulley off yet, I am hoping I just sheared a keyway and the pulley bouncing back and forth is what the banging noise is. Compression checks out good in all of the cylinders so I do not think I bent any valves.
Anyhow, here are some pictures of the engine and my helper, Xesia, working on it.