Is there a convenient way to tell from the outside whether an engine is a rod-bender or a 3.0l 603? I know it probably should be obvious -- but my understanding is that the engines are essentially indistinguishable externally. There's certainly nothing like a convenient "3.5" or "3.0" marking anywhere that I've found.

The reason I want to know is that, in response to my gradually worsening head crack symptoms, my dad and I pulled a complete 603 engine from Pull-a-Part in Winston-Salem last Friday over spring break. It's at home now, and we'd rather put the (hopefully good) #22 head from it on our known-good 3.0 bottom end, rather than just swapping in the whole thing as an unknown. Is the block part number a good enough identification to tell? Is there some clue that I should have spotted but didn't for lack of knowledge? It certainly LOOKS like our 3.0L but... if it was only different internally, then how would we tell? The kind donor was an 87 300SDL with 420,xxx showing on the odometer -- which leads us to not be entirely sure it was the original engine sitting in the thing. It probably was, but... who knows. #22 seems new to be on an 87 unless it was a replacement.

long story short... how do I tell whether that thing is a rod-bender or a 3.0? We're only using the head in any case, but it would just be nice to know.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL