Some follow-up thoughts ...
 

OK, I've driven the car for about 60 miles since getting it back ... a mix of highway and city, and not very hard, because it makes me nervous. Further thoughts on the noises, which have not subsided:
One thing that complicates this is that it's very hard to "separate" the two noise issues. There is a distinct ticking, which I am starting to believe is a bum lifter ... it's just "tap, tap tap," and speeds up to a rattle as the rpms increase. It is not an injector, and I don't think it's a worn bearing because this car's oil has repeatedly tested completely in "safe" ranges on metal traces. What else goes tap tap tap?
The OTHER noise is, as I mentioned the buzzy sound of the engine revving. It's probably not as violent as I first described, and it's hard to really describe, especially because it's partially drowned out by the afforementioned ticking. It's not even that I'm positive it's a bad noise ... it's just that it DOES NOT sound like what my car used to sound like ... it's a different pitch/tone.

Another note: This may be a complete "placebo effect' type thing, but I feel that the car is less responsive than it should be. It feels sluggish. Now, to be honest, it might be sluggish because I'm subconsciously not hitting the throttle as confidently as usual, and because the noises make it sound like the car is struggling, even if it isn't. But if it were a lag in performance, wouldn't that be consistant with a timing issue? I also noticed a puff of white smoke on startup yesterday morning, which I don't usually see in warm summer days ... very brief and no smoke when driving, but thought I'd mention.

One more question: In my diesel repair guide, it says that whenever lifters are replaced, the cam MUST be replaced as well, that you can't put new lifters with an old camshaft. Nobody here mentioned replacing the cam, so I'm assuming maybe this book is not referring to vehicles w/ overhead cams? It is really intended to refer to large trucks, so I know it doesn't all apply, but I was just curious.

This is in an ideal situation. It is also to remove liability from MB in case the cam/lifters are not compatible or either is damaged in some way.

The lifter on an OHC engine is not 'Profile ground' or domed like a follower for a rocker/pushrod style cam/lifter.
The pushrod type engine lifter is ground to encourage the lifter to rotate as the cam wipes over the lifter and to mechanicaly wear together and work harden.

Early MB cams also had different material in the rocker pad that was not compatable with the later cam material.
VW has had problems in the aftermarket supplied cams and lifters not being compatable.

A direct acting cam to lifter engine does not require the domed or taper grind as the cam lobe is offset slightly over the lifter and the cam wipe rotates the lifter/bucket and hopefully, the valve.

I have seen cam lobes that are tapper ground when new ( at the nose) but it was only 0.002" thou' across the nose.

Obvously, if money was no object then always replace the lifters and cam as a set.

Chevy/Ford/Dodge OHV type engines must be done this way because wear patterns and work hardening would not allow old to wear with new.

If your cam was in good shape with no pitting or ramp wear, new lifters should work just fine with your camshaft.


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Thanks for the thorough answer! That clears it up for me a lot.

Only if the cam is in bad shape. If no scoring is present there is probably nothing wrong with the cam. The problem with replacing the cam on a 603, other than it being $300, is that there are no cam bearings. The caps that hold the cam down are the bearings, so they would probably have to be replaced and re ground to fit the new cam.

It sounds like it may have either jumped time, which I guess is possible but somewhat unlikely. I bet the buzzing is TC related. He had to un tension the chain to remove that came sprocket, old stuff doesn't liked to be moved. Maybe one of the guides got chipped or something.

Any chance you could post a audio clip?

Hattie brings up a good point. It is probably timed incorrectly. When I put a timing chain in my '87 300SDL I missed by a tooth or two, it did not sound very good and was low on power. I would have the cam timing checked.

All symptoms of injection pump timing
 

And if your indy is as you stated and is one of the few techs or mechanics who try like hell to gain the absolute confidence of his customers in his ability to maintain and control these OM603 powered cars, then the problem is simple. Just have him to re-check the camshaft to crankshaft timing using the timing mark at the cam shaft tower (at 0 on the crank on compression stroke, the mark at the camshaft should be on spot), while simultaneously checking the injection pump timing. The camshaft, the crankshaft, and the injection pump MUST all be in sync, before you can get that "light sweet metallic sound" that you are listening for that everybody who has heard it knows what I'm talking about (assuming the head isn't cracked, and they usually don't just crack overnight in the shop during a lifter replacement job, either)

BenzDiesel

When my 617 "jumped" one tooth and retarded the cam timing I got a LOT of black smoke as well as being low on power. It wasn't subtle.

Maybe mine was jumped the other way.. yours may have been advanced and mine retarded.

Also, my IP timing was probably off (after part of my vacuum pump was caught in the chain).

I'll try to do so tomorrow, although the sound quality will be pretty bad. I don't have a digital sound recorder, just the old-fashioned tape cassette kind that I use for interviews. It picks up a lot of outside noises and feedback. But I'll make a tape and play around. By the time I figure it out, hopefully my car will be fixed. :o

Another thing: car is a bit awkward on startup ... cranks a little more than before and then sounds rough for two or three seconds before smoothing out. Then as soon as I touch the throttle, the ugliness commences. Before it started perfectly (in this weather, at least).

That pretty much confirms (to me anyway) your cam timing is off. I'd drive it over to your indy ASAP and not drive it until retimed if at all possible.

Ditto that. It really sounds like the injection pump and/or cam timing is off.

A master mechanic once told me: If it worked before and doesn't work now, where were your fingers last.

Sage words of advice.

Again, thanks. My dad concurs with the timing theory, and it is consistant with what bits of knowledge I have ... so I hope you guys are right (since that's fixable). I did not drive it today, and am taking it over to the indy tomorrow.

One Q: Upon rechecking my last oil report, I did notice that there was an increase in lead ... from 2 to 5 ... the report said this was not a concern, but did make note of it. That was in March. If it were from a bearing, would that bearing go downhill that fast? I did not have a report done on my last change. Wouldn't a bearing that was bad enough to cause a noticable noise change leave significant traces of metal in the oil?

Back and better than ever!
 

Just an update: I took the car back to my indy, and he said it sounded like a timing problem (I had my dad drive the car and he agreed it was definately a dog ... and you should have seen the black smoke that came out when he goosed it across an intersection). So my indy said he'd check the timing, replace the chain, etc. At the end of the week I got it back QUIET and FAST. :D He replaced the chain, removed IP and reset the IP timing, and it is one happy engine now. After all that worry and discouraging frustration I had over this, I'm very happy to have my car back and even smoother than before!

Thanks for all your help, as always ...