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Thread: NYC w201 + 3.0l m103 + 717.404 = :)

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    Join Date
    Apr 2016
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    New York City
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    NYC w201 + 3.0l m103 + 717.404 = :)

    Trying my hand at a build thread to document, albeit very slowly, the progress on a car. This is my first W201 and first Mercedes. We live in NYC where car ownership is pretty unnecessary, let alone car projects, and where the simplest things like finding a particular metric bolt can be a triumph. Updates will come slowly, but I figure since this forum is pretty sleepy with posting…I’d post slowly. Hoping people find this entertaining and informative, and I’m hoping I can learn from anyone with more experience than me that wants to chime in.

    So, I have this car. Its a 1991 190e 2.6L w/ a manual transmission from the factory (717.432). The engine is slowly dying but it's chugging along. It's burning oil and something is causing the CIS-E to remain in open loop, but that's another thread.


    And I have this transmission, a 717.404 from a 16V that allegedly had ~60k on it before being totaled and parted out.


    And lastly, I have this engine, a 1987 3.0L M103 (103.983) with 46k miles on it.


    I wanted to first examine the health of the engine so I pulled the valve cover to examine the cam and rockers and also conduct a leak-down test to see how each cylinder was sealing up. I know there are conflicting opinions about conducting leak down tests warm or cold, and most sources suggest conducting them warm. Since this engine is out I’m gonna have a hell of a time warming it up so a cold test it is.

    Pulling the valve cover off an engine for the first time never gets old. It’s the easiest thing you can do to marvel at the inner workings of an engine. Initial inspection of the cam lobes (looking past the towers and rocker arms) looked promising. I’ve recently learned of the softer cam/rocker material used in these early m103’s.

    On to leak-down tests. I don’t have any photos of the actual leak down testing because I had one hand holding the wrench on the crankshaft to prevent the engine from turning over, and the other hand was struggling to connect the air fittings. The results were a bit disappointing.

    Cylinder 1 - 15%, good
    Cylinder 2 - 45% leakage from the exhaust valve
    Cylinder 3 - 50% leakage from the exhaust valve
    Cylinder 4 - 60% leakage from the exhaust valve
    Cylinder 5 - 80% leakage from the exhaust valve
    Cylinder 6 - 10% good

    I conducted the tests multiple times and got pretty consistent results, even after a squirt of oil into the cylinders and "rocking" the piston around TDC. The air leakage was very obviously at the exhaust manifolds, which were still attached at the time of testing. I could feel and hear the compressed air leaking past the exhaust valves.

    I then had a second look at the plugs and 2-5 were slightly oilier than 1 & 6, another clue pointing to the health of cylinders 2-5 that correlates with the leak down tests. That's plugs from cylinders 1-6, from left to right. Notice how 1 and 6 are slightly drier.

    I pulled the exhaust manifolds and got further signs for the health of cylinders 2-5 by looking at the exhaust valves. Looks like 2-5 were burning oil from a valve stem seal leak, I'm assuming. 1 & 6 were visibly cleaner as you can see, but not far behind because it looks like some oil was just beginning to leak down the seals (top row is cylinders 1-3, bottom row is 4-6)

    At this point I'm asking around for machine shops in the area for a valve job, and I went forward with the disassembly.

    Pulling the rocker towers


    Rocker arms and bearing surfaces look great.



    No scoring or marking on the camshaft lobes or journal bearings. The lobes still have a mirror finish. It’s a shame these are most likely the earlier softer cam and rockers. How does one definitively ID the softer cam and rockers?




    Inspecting and removing the timing sprocket, chain guide pin, and removing the camshaft. Chain and sprocket look good.




    Journals look good also.




    Off with it's head! Happy to see the cross-hatching is still present in the cylinders.





    A look at the valves on the underside of the head didn't reveal any severely burnt valves. I'm hoping it's just carbon build up that's preventing the valves from seating pproperly. Cylinder 5's 80% leakage had me expecting much worse.




    That's about all I got done this weekend. I'll need to find a machine-shop in the area to do the valve job, cleaning, valve guides, stem seals, and possibly resurfacing.
    I had initially considered putting in a mild dbilas cam, but I'm now having a hard time justifying the cost of 12 new hardened rocker arms, especially since the stock cam and rockers are in such decent shape. Another option is I could also look for someone to regrind my 'soft' cam but don't know if it's worth it to alter these camshafts. Last option is just to put the stock cam and rockers back in and be ultra mindful of oil levels and use a good high zinc oil. The car is only a weekend driver after all. In any case I have some time to decide on the cam and rockers while I wait for the valve job. Beyond this engine work I'll be mating the getrag dogleg to the motor, most likely using JC's flywheel and clutch kit. More to come on that soon.

    Here's a parting shot of the car parallel parked in its native NYC habitat on Canal St.
    Last edited by rolandtiangco; 07-23-2017 at 08:11 PM.

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