I had a 3.8L gas MB engine jump time and piston(s) met valves. I pulled one piston and rod assembly and took it to a machine shop. The machinist looked at the underside of the piston for deformation and told me he'd replace it.

He'd been doing engine machine work for NAPA, wasn't an experienced hand with MB but he was near retirement after 30-40 years there so I took his advise. I really jury rigged the assembly because I'm poor. I bought a piston, tried it in the hole and it moved a bit so I assembled the engine and it ran fine for a while. I didn't frequent this site often and didn't know how to search the archives. I was a 50+ year old rookie.

The 380SE's of the mid 80s weren't nearly the engine as the diesels of that era so it didn't last long anyway but to my knowledge the piston was never the problem. It was fueling system and electronics which caused me to yank the engine and put an om617 in the body.

It seems to me if there are many such questionable pistons in consideration the probability that at least one of them is not worthy for use. I would be reluctant to assemble an engine using questionable components. No, I wouldn't do it so you should probably make sure by a more accurate means than asking someone to make a guess.

It just seems like too much expense and time to risk but I'm sure if you took photos of the tops and undersides of those pistons, posted them here and asked these good gentlemen you one or more of them would advise you with opinions as accurate and useful as you will find anywhere.

You will also need to try and stick to this thread, answer questions, ask for clarifications and make yourself available to those who can help guide you through this process.

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84 300SD
85 380SE
83 528e
95 318ic