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Rod journal discoloration

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Bock

5+ Year Contributor
94
73
Jun 13, 2018
St-Jerome, QC_Canada
Im tearing down my engine for a rebuild, notice some discoloration on the rod journal.

No hot spot/blueish tint and surface is smooth with like a cross hatch pattern.
I'll measure everything but i'll like your input. Crank look super clean.
I do not know the condition of the engine prior to disassembly and or the actual mileage.

**Crank bearing holder look darker on the right side but is due to shadow. It is like the left side, I was trying to hide the light to limit glare

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The bearings look like they got hot. And the bearing seats in the rods and block almost look like bearings spun in them before.

If I had to make a guess as to what was going on I would guess someone spun a bunch of bearings and then just got a new crank and slapped new bearings in without doing any machine work.

I would have a machine shop re-do all the rods (may as well get ARP rod bolts installed at the same time) and have them check the block too. I may be totally wrong on what is going on, the bearings may have just gotten hot and made the surface look funny, but any bearing seating surfaces I have seen are normally a lot "cleaner" looking. It's hard to tell from pictures.

Are the surfaces smooth when you feel them?

When you took the bearings out did they just fall out or where they held in by the outward tension that the bearing has? If they just fell out they definitely got hot
 
Bearing was still on crank, stick with the oil film. Surface is smooth without any scores. Had someone told me that can be oil stain. No sign of heat (blueish color) or anything like that.
Im waiting for my micrometer kit to measure ID. I dont know if i can gently rub the surface with a 1000/1500 sand paper with oil. If its a stain id should go right away.. whats your toughs?
 
Alex I kinda agree with @97egl . You can measure but the bearings should hold themselves in the rods so I would ask a reputable machine shop to just resize the rods and if you wanted, press the rod bolts out and go ARP, perfect time. We did that to a stock 6 bolt set of rods that had a special oil shedding coating on them and threw a NGR piston set in it since I didn't have a good set of used pistons. I'd weigh the assemblies and write it down to see how much the balance gets off when they resize them. A GOOD shop would do that for you to keep them super close for rotational balance. I do it for all my motors. Then you can feel super confident on your bottom end lasting a long time. The crank looks great just make sure it is within spec with your bearing selection and it should be a very nice motor.
Marty
Here is the build sheet on that motor for reference. It has a Kiggly Girdle in it also.
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Bearing was still on crank, stick with the oil film. Surface is smooth without any scores. Had someone told me that can be oil stain. No sign of heat (blueish color) or anything like that.
Im waiting for my micrometer kit to measure ID. I dont know if i can gently rub the surface with a 1000/1500 sand paper with oil. If its a stain id should go right away.. whats your toughs?

Since the oil film was sticking the bearing to the crank I would clean all the oil off the rod and bearings and stick the old bearings back in the rod and see how easily they come out. If they don't just fall out that's a good sign.

If everything feels smooth that's also good. It could just be oil staining like you mentioned. It's very hard to tell the condition of machined parts from pictures. 1000 grit is fine you could even go to a lower grit. It takes a lot to actually remove material on a block. If all your doing is a quick buff to check if the stains come off you'll be fine.

You said your waiting for a micrometer kit. If your buying one and haven't used one before measure several time. And always measure and write your readings before looking at the spec. It's very easy to find the readings you want and not what's actually there. If you know how to use one ignore this part. You probably can measure better than I can. (Ask me how I know not to look at the spec first. HAHA)


Overall I guess you have to decide what your comfortable with. I myself would probably have the ARP bolts installed just because it's an upgrade and at least you know your rods are good after the machine shop takes care of them. I would bring the block with when you have the rods done or even just the main caps and ask them what they think. They'll be able to see it better than we can.
 
@97egl

Did some test, with everything clean, the bearing hold well in the rod/cap. Nothing loose it hold like a new bearing would.
I tryed some P1500 paper with engine oil and gently rub one cap. It really look like oil stain. Paper got instantly black and cap shine again.

Here is some pics
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This is good news. Keep us posted! :thumb::thumb:
 
Wonder if that’s from the goo that get trapped in the oil passage in crank but why is it on the underside of the bearings???

Alex, clean out the oil passage in the crank before you put everything back together. I taped one side and soaked seafoam over night. Then used 2 cams of brake cleaner and compressed.
 
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