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I wonder what that black fluid is. Does it look like high-mileage oil?
I would try to hand-polish the crank to smooth any rough edges around that scratch. Like use an emery cloth (or very fine wet/dry paper) soaked in a lightweight oil.
You should use Plastigage to ensure the bearing's tolerance meets factory specifications.
Thank you. I will try polish and focus on the scratch only - leaving the rest of the bearing untouched by the polishing material. I wasn't going to plastigauge this, but I think I may have to do so after the polish is complete.
Fortunately, this is a 'brown' bearing journal - so I have two sizes up to play with (black and blue).
The black fluid is really stumping me. It was also on the bottom of the sump. It can't be high mileage oil - I usually change my oil between 600 and 2000 miles! A friend of mine said it could be old assembly lube from the factory - I am worried it is the top lead layer of bearing material!
Save for this unfortunate scratch (which I have now determined to be user error) the job would have been worth doing based on the condition of the Cyl 2 bearings alone.
The black fluid is most likely residue from the blind holes in the Crankshaft. Every crank shaft is cross drilled several times to create the oil channels for the Rod- and Main bearings. The Holes gets plugged at the the end, creating partially blind holes.
The heavier dirt particles in the oil get collected in this blind holes over time by centrifugal forces when the engine is running. This is no big deal, as the oil passes the oil fliter first wich catches all parts big enough to cause wear before it reaches crtitcal parts.
When you look closeley at the crank, you maybe could see the plugs.
Reading through classic car magazines, this "System" is noted often. There where old Motorcycle engines wich relied on this as the only system of oil Filtering, there where bolts fitted at the end of the oil channels. The owner shcould dissasemble the engine, remove the bolts in the crankshaft and clean these blind holes from time to time. Mostly italian manufacturers used this system. Go figure you have to dissasemble your engine to do the job every 20.000 Miles or risk heavy wear on the the engine.
What a wonderfull, handy invention a Paper oil filter is...
I had a situation (non S2000) where two of the rod bearings were worn through to the copper; and those bearings were also gritty and striated around the circumference where the bearings had worn through. The rod journals were similarly striated underneath the bearing damage. The damage was vertical rather than horizontal, going around the circumference of the journal I sanded and polished out the imperfections - not perfectly - using the same basic method shown in this video.
My engine was disassembled, with the crank on the bench. The problem that you will have, working from under the car, is cleaning the microscopic debris, so I would do an almost immediate oil change after running the car.
In another situation (also non S2000), I had a new "ghost main" billet crank made for a 3 main engine. The only problem was that it conflicted with the oil pump pick up and distributor drive gear. The local machine shop did an extensive massage of the crankshaft to make it fit, and when I picked it up, there was a slight dent in one of the journal surfaces, smooth but visible. The dent was more horizontal than vertical. In any event I installed and used the crank for 2 plus years without any apparent issue.
In your case, my amateur advice is that you try to smooth out the edges s much as possible but not necessarily remove the divot.
I had a situation (non S2000) where two of the rod bearings were worn through to the copper; and those bearings were also gritty and striated around the circumference where the bearings had worn through. The rod journals were similarly striated underneath the bearing damage. The damage was vertical rather than horizontal, going around the circumference of the journal I sanded and polished out the imperfections - not perfectly - using the same basic method shown in this video.
My engine was disassembled, with the crank on the bench. The problem that you will have, working from under the car, is cleaning the microscopic debris, so I would do an almost immediate oil change after running the car.
In another situation (also non S2000), I had a new "ghost main" billet crank made for a 3 main engine. The only problem was that it conflicted with the oil pump pick up and distributor drive gear. The local machine shop did an extensive massage of the crankshaft to make it fit, and when I picked it up, there was a slight dent in one of the journal surfaces, smooth but visible. The dent was more horizontal than vertical. In any event I installed and used the crank for 2 plus years without any apparent issue.
In your case, my amateur advice is that you try to smooth out the edges s much as possible but not necessarily remove the divot.
Thank you - this advice mirrors the advice I received from the "bobistheoilguy" forum and a few of my friends.
All seem to think there will be no problem as long as the raised edges are smoothed out. I ran/sacrificed some new honda bearings over the surface to confirm no scratches to the bearing following the polish job.
I'm now waiting on additional bearings - fortunately I replicated my parts order from Yoshiparts with Amayama as I wanted to keep "spares" on hand and wasn't sure about the global shipping situation, so the job should be finished soon!
At long last I have finished the job and started the car today.
To my surprise it seemed smoother; but I did replace the spark plugs too.
Just replacing engine mounts and spraying some rust protectant and its back on the road.
Final summary of rod bearing condition in the pictures below.
Update: I have driven the vehicle 30km on the new bearings and all seems to be good despite the (repaired) damage I caused to one of the journals - still kicking myself over this mistake, but I have ran this past numerous people/AI and both seem to think that there will be a near zero impact on future reliability - Alas, I plan to replace the timing chain (for the hell of it) once I hit 200,000km (it will take a while) and I will replace the bearings again at this stage. Assuming the repair holds, we will see if additional wear is impacting the bearing.
I have noticed that I no longer see an oil pressure light for 1-2 seconds on startup.
I picked out one of the bearings in the above pictures and sanded it with 800 grit as an experiment - I could not get down to the copper material (assuming it is there) in any reasonable timeframe. This indicated to me that there is some substantial (but not critical) wear to cylinder 4 (above).
Accordingly, I recommend that owners replace their bearings at 100k miles (160,000 kilometers), especially if driven spiritedly/tracked. If not tracked or subjected to high load for extended periods of time, you could probably wait longer.
Changing bearings at 100k seems super excessive. Doing an oil analysis will tell you the approximate health of your bearings. Driving on track is something completely different, but I have buddies tracking their cars at 180k miles with good bearing health. It comes down to maintenance. If the car saw excessive oil temps, the bearings will wear faster than if not. You can track a car for hours and as long as oil temps stay low, the bearings should theoretically be fine. The worst time for bearings is on start-up when cold when there is no oil pressure. But oil quality and temperature is the key factor here.
If someone is tracking a car and seeing high temps constantly, the bearings will wear faster as the oil shears and stops lubricating as effectively. This is why an oil cooler is a great upgrade for people who track a lot. Also adding oil pressure and temp sensors/gauges as insurance helps a ton.
