What is making that sound (some sort of engine knock)
 

What do you think might be causing this sound:

http://www.youtube.com/watch?v=s2pEM3fAepw

I adjusted the valves, corrected chain stretch (installed a 4 degree key), played with the rack dampener bolt, and rebuilt injectors with new nozzles. (No, I didn't test or balance them)

This knocking sound just does not go away. It is the same as it was when I first got the car.

The idle is nice and smooth, and I was very impressed when I took it out on the interstate today. it felt powerful and not loud (and I could not hear the bloody knock at 60 mph).

Normal sound?

Should I keep obsessing about it??

Narrow Down the location
 

by loosening each one of the injectors (Individually) with the engine running...
the one that stops the "Knock" may be your problem area.

OR

Mechanics Stethoscope to be able to locate the noise.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41966

(I don't like the sound of that!)

Yep, that's the stethoscope I have... the knock seems to be closer to the front (i.e. 1, 2 or 3). Going to try the removing injector line nut one by one thing and see if I can narrow it down.

What sound do you not like?

Nature of the beast, I replaced a motor that was knocking like that. Looking back I shouldn't have, I drove with a knock for many many miles. If I were you I'd enjoy your car and not worry. I know the noise is annoying (yeah it is I am a perfectionist) but I think you will be fine if you just let it do it's duty...

What am I listening for? That engine sounds normal.

Sounds exactly like my engine....

my 82 300SD engine has 220k kms on it, barely broken in lol and it has abit a knock sound like that too, my chevy 6.5LTD has a knock like that too when its cold? i think its just diesel thing, tried running some purge through it yet?

My best guess is an injector. See if you can identify a specific loacation. Have you ever had the injectors checked/ replaced? How many miles on them?

I think you may have answered your own question - to an extent.
You're one of us now, you have an antique car with a diesel engine YOU ALREADY ARE OBSESSED;)

Yes, I am!!!

I found this video on youtube http://www.youtube.com/watch?v=tOhLBkBR1k0&feature=related

Title is 'piston slap', this is the closest sound to mine that I was able to find...

Piston slap articles
 

http://dspace.mit.edu/bitstream/handle/1721.1/15728/09216886.pdf?sequence=1

interesting stuff...

Sounds to me like typical "nailing."

http://www.youtube.com/watch?v=dseUEVVGsAw&feature=related

I'd try some Diesel Purge!

If you can narrow it down to a particular cylinder that way, then you could swap a couple of injectors to see if the behavior "goes with the injector".

ENGINE KNOCK
 

I had an old 240D that knocked until i replaced the vacuum pump. Good luck!

well i thought mine sounded like that but ill let you be the judge.

http://www.youtube.com/watch?v=V_jLKHKxOGc