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Old 12-04-2011, 04:39 PM
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Location: Baltimore, MD
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Here are some pictures of the crank with the bearings off. They feel very smooth but I do feel a scratch on one of them. I measured the size it's right on 51.95 mm. I will plan to measure the others tomorrow. If they all measure within spec, I'm going to order new bearing and start putting the motor back together.

I realize I can break the motor down farther and measure every piece but I'm going to take the risk that everything else is within spec.

The compression was mid to high 300's on all the cylinder except #3 that had the bent valve.

When I removed the upper pan, I didn't see any sludge. Should I pull the oil pump and clean it? I did have oil pressure so I think the oil pump is working properly.

Thanks for all the advice.

Attached Thumbnails
connecting rod bearings look worn-imag0344.jpg   connecting rod bearings look worn-imag0343.jpg   connecting rod bearings look worn-imag0345.jpg   connecting rod bearings look worn-imag0346.jpg  
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Old 12-04-2011, 05:00 PM
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Location: Lafayette Indiana
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Did you measure from different directions so you could see if it is egg shaped? If the crank mics good I would take it as a minimum to a shop and have it polished. I would have them clean out the oil passages too. If they find a lot of bearing debris in there you will need to consider cleaning the oil passages in the block too.

It is so much work to pull one of these apart and reassemble is is a shame to cut corners.

I would also have the machinist look at the oil pump too.
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual. It still needs upholstery redone...I also have a 427 Cobra replica with an aluminum chassis.
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Old 12-04-2011, 06:10 PM
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1,2 and 4 all show Visible signs of Damage (Scratches)

No need to discuss #3.

Needs to be "Polished",
'Crank should have a "Mirror LIKE" finish on it.

I'd HOLD OFF on ordering the Big End and Crank Bearing sets,you may be going with #1 Oversized.

ALL of the advice from the Replys before this should be followed.

Not that much more work or expense.

AND if you've got Debris/Swarf in the Internals,THAT doesn't get removed.

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his way with your 617 Just when you Don't need it!
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Old 12-04-2011, 06:11 PM
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Location: Nova Scotia, Canada.
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Since the crank journal is not torn up. In a way the bearing appears to have done it's job by sacrificing itself to the foreign material.

The question in my mind is where did the material come from? The bearing itself shedding material? If that much was coming down the oil passages some of the other bearings should have at least got a portion of it.
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Old 12-04-2011, 06:43 PM
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1987 w124 300D
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Old 12-04-2011, 08:07 PM
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it looks like you have only pulled the rod caps... I'd pull the main caps and look over THAT set of bearings... debris came from somewhere.
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Old 12-04-2011, 10:53 PM
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There is an old trick that does work on a good crank to polish it. Take 600 grit try-m-ite paper, oil it, wrap around the journal, then take a flat shoe lace wrap around a few times, you should have a least a foot or more left over on each end to grab. pull back and forth a bunch of times, try to cover all area equally. This works quite well just for polishing, will not remove deep scratchs. The forth picture would be a canidate for this assuming it is round. The rest, well maybe you can get away with it.

Must say getting the crank ground is only about a $100 or so. So you may be a little penny wise and pound folish to not just take it to a shop and have em fix it up right.
1977 240D turbo
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Old 12-04-2011, 11:03 PM
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Looks good to me

The crank journals look pretty good , should polish up nicely. I would bet that new std size bearings will work. I am still a fan of plastigaging the journals , it is an easy thing to do and as has been pointed out the average guy is usually not skilled enough to get reliable readings from the crank journals and inside mic the bearings. By all means get the bottom end checked by a machine shop. The bottom ends of the rods should be checked for size as well since they can become deformed. Cheers Dan
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Old 12-04-2011, 11:27 PM
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I'll pull the crank off tomorrow and bring it to the machine shop to get polished and mic'd. Thanks for all the replies.

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Old 12-18-2011, 11:14 PM
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I received the crank back from the machine shop. He said it showed little wear and was definitely in spec. He seemed to be impressed with the quality of the 240d motor.

Do the notches on the end caps have to match up to the notches on the connecting rods? e.g. the notches are both on the same side

Also can someone confirm that the torque on the end caps should be 40-50nm?


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