Got a clacking in the ol' slug (1983 240D)

I've done a diesel purge (twice), replaced the injector nozzle from where the sound seems to be coming from 4th cylinder at the oil cover), adjusted the valves (lifters).

I even just replaced the front left wheel bearings, in case they were clacking... but no, it wasn't them.. (they needed replacing anyway)

So what is the clacking noise in the movie file at www.pauldrayton.com/uploadfiles/clacking.mpg ? (It's a 13 mb video file. A small audio only file is at www.pauldrayton.com/uploadfiles/clacking.wmv for the bandwidth challenged). The sound gets worse when you ride around for a while.

When I had the oil cover off while doing the valves, I noticed the bar that goes across the top, above the camshaft, has some play in it at the far end. But nothing that could clack like it does. I didn't know how tight the chain at the front should be (is that the timing chain?), so I couldn't really check it. The sound doesn't seem to be coming from the front though. I've listened with a piece of wood all around the engine. The only place I have heard it as on the oil cover at cyl 4.

Could this be the famous nailing? I didn't adjust the bozio nozzle I bought - I just stuck it in. I don't have shims to adjust them anyway - still waiting for the stealership to get them from Deutcshland uber alles. If this is a injector issue, then fine, I'll get them adjusted properly.

But it sounds like something moving and perhaps even slapping. Heck, you listen to it and tell me. If a picture is worth a thousand words, then a sound is probably worth about 435 words, so I'll stop typing now.

Some advice would be great. This is my work car and I want it working!

Thanks