So I spent some time at my mechanic's shop today, and helped pull the head ( a #22 by the way, now that I could see the casting mark clearly). First things noticed- The head gasket was perfect, no sign of any problems there. Proceed to looking at the piston crowns and bores. Since #1 is already at TDC, I saw a very light, uniform carbon soot deposited over its surface. Number 2, the real problem cylinder- dead clean! Number 3 was also pretty clean, while 4, 5 and 6 were nicely carboned like #1.

All cylinder bores look fine. No ridges, scoring etc. Just what a good bore should look like, so we rotate the crank to look a little deeper. As #1 descends, I watch #2 come up to TDC and guess what? It is at least 1mm shy of where it should be! A friggin bent rod! Number 3 appears to crown slightly off kilter, but crests the bore. 1, 4, 5 and 6 all fine.

There it is. I'm assuming the fact that there is so much head space between the piston crown and the head explains the low compression and lack of ignition. In anticipation of a fatal flaw, I found an OM603.96 with 140k miles. I'm going to listen to that engine tomorrow, and if it is as described I'll acquire that engine. My plan is to freshen it up with a set of rings, swap over all the good bits like the head and injection pump from the 3.5 and end up with a solid car. I will be searching the site for threads on this swap, but please, any tips as to what I should be looking for, what changes I need to accomodate etc. would be SO welcome!

There is nothng like diving into mess like this to really learn a lot. While it IS pretty inconvenient, I know that when I'm done I will have a 126 that I can have real confidence in.

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Chief

1991 350SD