I am unsure but have to almost conclude. The responses so far at least. Are partially based on how well your pictures are displaying on members monitors. The reproduction I get is pretty clear that real heat was involved on the rod caps. Also on my monitor the main bearing caps look normal.

The computer I am using is average in my mind. As is the monitor. I have questions about me as an observer but that would be subject to another thread. Perhaps different service providers. Have different qualities of transmission. Individuals color perception also may enter into the picture as well. I use the American spelling of colour to not confuse Americans.

I am interested in what the crank journals are like. I do know that I would be checking the connecting rods for concentric big ends. At least that is a relatively inexpensive issue if it needs addressing.

I would also plasti gauge the rod bearings now. I assume the plasti gauge product is the same. Yet perhaps sold under another name in England. Whatever bearing clearance is present and what the surface of those bearings and journals look like. Can tell a lot in my opinion.

If for example the rods bearings where replaced everything might still be excellent. If the bearing clearances are normal and all appear well. visually. I would not replace them. Checking the main bearings in a similar manner of course.

I am a Canadian and I suspect some of my ancestors where so cheap. They probably swam across from the old country. It is thought by my parents that I am a decendent of sir Francis Drake as well. I never bothered verifying it.

This is one i found .They all looked the same no sign of overheating.Your picture of engine no 1

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Thanks to everyone for the comments, and in particular thanks to 97 SL320 for leading me down the path to enlightenment.


It seems the crank journals and con rod caps were subjected to an Induction Hardening process. This particular OM 603 is from a British Army BV 206 which has been through the Army Base Repair system, so I'm not sure if the process was done then or whether all OM 603's are like this straight from Mercedes.


As for the rod movement, 97 SL320 is correct, these engines have piston guided rods.
Interesting stuff, I enjoyed reading up on the subject. :-)