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

if it's an 87, it's a 3 l, unless the previous owner put a 3.5l in for fun...
86 and 87 is 603.96x and is a 3L
90 and 91 is 60397x and is the 3.5L that everyone is scared of.

Id do a leak down test, and if the engine holds pressure drop it in...

Why was the car in the junkyard anyways??

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All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic

aren't there electronic components on the .971 IP? of course if it was in an 87, they would have used a matching IP for the car if they put in a .971...
Odds are very good that the original #14 head cracked, and the PO of the 87 had it changed...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I can understand your dilemma, could be a used engine in that car.

You might need to wait for GSXR or Sixto on this one. There are things such as the newer timing-chain cover that might indicate a 3.5L, but could have been replaced. The IP is externally the same on both engines, except for the part number, difficult to tell.

Is there a part number tag on the block in the IP area or on top of the flywheel area?

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Gone to the dark side

- Jeff

The flat surface which should have the part number is totally flat on my engine, there is a small black tad riveted to the bellhousing, though.

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.