80' diesel rabbit problem while revving

[MK3dub951]

as the title says i have a 1980 rabbit 1.5l diesel. i bought the car with the head taken off of it. the PO was pretty much clueless about the car and tore it apart for no reason. it sat for a few years with the head unbolted but sitting on the engine. i cleaned it all up and got it timed and running sort of . while idling it is fine. once you rev it to a certain rpm it sounds like something lets loose and it clanks. ive checked the oil filter for metal and changed the oil a few times. put an oil gauge to make sure it is getting pressure (at about 120 PSI) checked and re checked mechanical timing all is good. just can not figure out the noise. i have a video on youtube of the car running search "80' diesel rabbit problem while revving" posted by MK3DUB951 i can not post it on here for some reason. any input would be great. oh and this is my first diesel but i have had quite a few gas VW's  once again thanks! hope to figure it out soon .

[air-cooled or diesel]

shut her down; you have to find source of this clanking. find timing marks and turn engine over 2x by hand. if anything has given out in the engine running it will guarantee a bigger repair bill,,pull valve cover and oil pan and take a good look; after pull injectors and rotate engine so you can see down the bore/top of piston and take a look(did anyone say light?). when you rotate engine its just enough so you can see part way down the bore, by the book its where all 4 pistons are at the same height, 1/2 way down the bore

[MK3dub951]

Thanks. That's what I figured I was gonna have to do. Going to pull the pan look around and prolly pop off some end caps to check rod bearings . Hope it is not that but prolly
The most likely culprit

[air-cooled or diesel]

before you pull injectors i think you will need a bentley, inj themselves use a special socket, and are removed/installed in a specific way; otherwise you can end up ruining your head.

[MK3dub951]

Thanks. I have a Bentley and it's like a 27mm deep socket .

[ORCoaster]

Measure the clearances of those valve shims!!!!  I had my head done by a "Professional" and somehow he got distracted from what he was doing and had two of them a bit too close to the top of the piston but it seemed to only really tap on revving the engine.  Not when you rolled it over by hand.  Something to due with the dynamics of the cam?   Or tension on the belt.  I was not happy to have paid what I did only to have the top of two pistons rap a tapping once I got it going.  Oh, this was a mechanical head too. 

[MK3dub951]

That sounds more of what's happening . It's a mechanical head . The cam followers are shims . The head had been apart possible the flowers could be miss aligned and shimed wrong ..?

[air-cooled or diesel]

i had a similar prob 1 time; it was a hyd head, but thats not the difference here, as it turns out my timing was off a little, well i turned engine over 2x and was ok; start it up and soon enough i threw timing belt; ended up having to use right mark(after buying a new head, etc.). turning engine over 1-2rpm by hand and starting up @1000rpm and + certainly dynamics 'change' , tolerances will be even smaller.

[MK3dub951]

Good to know new to the forum and parrentlly I found the right place to ask the questions . I will dig into the motor more next weekend. The noise sounds focused around the intake manifold. Put a stethoscope on the block was hard to tell but still the amount was louder when listening to the head . Still gonna pull the pan and pull rod ends off to at a min eliminate a possibility