If you are as bored as I was a few winters ago you might want to look here =>

OM617 (non turbo) cam profile specs, piston height specs etc

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Thanks. I'll check that out.

OK, happy update.

Following all the advice here, I picked up a new jam nut and cap nut from the MB dealer.

Then I did the following:

1. Pulled the valve cover and the air cleaner.
2. cranked the engine so that the crankshaft indicator showed "0 degrees". I also checked the position of cylinder 1 cam lobes. Exhaust was pointed horizontal to the ground, with the tip of the cam facing towards the driver's side of the car. The intake cam lobe was pointed at about 30 degrees towards the passenger side.
3. Using a hex male socket, removed the two bolts holding the cam rockers in place for Cylinder 1 and 2.
4. Pulled off the cap nut for the exhaust valve for cylinder 1.
5. I was in the process of putting a needle-nose vice grip on the valve stem (through the valve spring. There was a small moment of PANIC, because at this point, the jam nut simply 'popped' off the stem... yep, it was completely and utterly stripped! Good thing I had stuffed clean rags all around the timing chain, or THAT would have been a DISASTER!
6. Pulled the spring keeper and the spring off.
7. Examined the valve stem, which had dropped down about 3/16 of an inch, and was sitting on the top of the piston! The threads were 95% OK, but it was clear that one thread needed 'cleanup'.
8. Looking at the threads, I believe it is perfectly salvageable. Reason is that only 1 thread requires cleanup. The threads for the cap nut are perfect, and the threads for the jam nut will be 80% OK if I use a die and 'clean up' the threads.
9. I go to Ace Hardware store and get the right die. You need an M10mmx1mm thread pitch. I bought the "Irwin" brand die. Nicely made. They also own the "Vice Grips" brand.
10. I used a needle-nose vice grip to carefully hold the valve stem while I ran the die down the valve stem. I was able to, with patience, clean up the threads nicely. As I mentioned, only one thread for the jam nut needed 'cleaning'. All the other threads were fine.
11. Ran the die all the way down the threaded portion of the stem, and then back up. Very little material was removed. In fact, I could hardly see it.
12. After cleaning with a clean rag, did a careful visual inspection of the valve stem. Looks good!
13. Put the spring and spring cap or keeper back on, then pushed the spring cap down and threaded the new jam nut down as far as it would go. I then used my Hazet '3rd wrench' to hold the spring cap and used a 14mm ratcheting box wrench to run the jam nut all the way down the threaded portion of the stem.
14. I then put the new cap nut on.
15. Moved the engine so that Cylinder 1 and 2 valves were all closed.
16. Popped the cam rocker towers back into place. Tightened the bolts. (I tried to put the cam rocker towers back with one of the valves open... it's pretty impossible... I had to close all the valves and relieve the pressure off the valve springs to get the towers back in.)
17. Put the valve cover back on!
18. Check for any loose parts, fired her up!

THANK YOU for all the great advice. The fear of dropping a valve into the cylinder is real and made me hesitate for days. Once i decided to do it and followed the steps as noted above, it went smoothly.

In fact the thing that took the most time was simply trying to get the die from NAPA Auto Parts on the top of the valve stem evenly. I never could do it. The design of the die, coupled with the 'notch' in the valve stem, makes it REALLY hard to line things up without fear of cross threading with the die!

I ended up going to Ace Hardware and getting another die, this one from Irwin, which has a MUCH better design. The design of the Irwin die allows you to really line up the die properly on the top of the valve stem.

I spent the most time slowly turning the valve stem using the vice grips and holding the die with a flat-jawed pliers. I didn't want to nuke any of the good threads, cross thread it, or remove too much material. Success!

Thanks so much you guys! The white 240D is repaired at minimal cost and it is running really well!

Packman

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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

Good call not struggling on with the cheapo die - some of those cheap things are pretty horrible.

I'm glad to hear the trauma was a success.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!