Strange marking on rod bearing after install
 

Hi team,

I installed my rod bearings on the weekend in order to check clearance on my crank using plastigauge.
When I removed the rods to check out the plastigauge readings, I spotted these markings on this bearing only. I'm referring to the oval mark near the top/edge of the bearing.
Has anybody seen this before or know what causes it? I assume it's a low spot in the bearing? Is it anything to be concerned about? eg. does the bearing need to be replaced?

https://lh3.googleusercontent.com/wh...M=w522-h694-no

Thanks,

Look at the crank. Is there an oiler hole there?

Sent from my SM-G928V using Tapatalk

Ha! That's exactly the shape of it!
Duh! Surely that's going to be what it is!

hahaha - now I feel dumb (er than usual!)

Thanks! :)

This is how we learn. Keep asking and keep learning. :)

I hope you had the big ends re-sized.

Agree, you're always going to have some marks with dry PG, but that looks a bit tight.

Listen to Mr. Steve!!!!

Whatever you are showing, beam or cap, it looks like the rods have not been resized.

Unless the machine shop is charging me for something they didn't do, (unlikely) then I 100% had them resized.
It was clear that the inside of the big ends had some attention, as the new metal inside was nice and shiny.

Given that I have no experience with this, what exactly is it about the photo that gives you guys the impression that this hasn't been done? Is it possible that you are looking at the marks caused by installation? The machine shop measured everything for me and advised that standard bearings would be fine.

Just for peace of mind, I measured what I could myself afterwards -i measured the bearings myself with a balltip micrometer and according to my notes they all measured at around 1.489 - 1.483.
The bearing journals on the crank all measured at about 52.973 - 52.975. (assuming my micrometer is accurate.) I got a bore gauge on ebay - but after playing around for about an hour I couldn't get a proper reading on the big ends of the rods. So, I went for the plastigage option. Admittedly they came up on the tighter end of the scale.

https://lh3.googleusercontent.com/__...Y=w522-h694-no

https://lh3.googleusercontent.com/xT...w=w925-h694-no


The other possibility is that these are ACL bearings, which according to their website use a slightly different process for finishing their bearings. I'm not sure if this could possibly give the appearance of a tighter clearance on the bearings after dry install?

From their website:

The RACE Series performance bearings as manufactured have
an appearance that is a dark tarnished colouration, which can
vary from dark black/brown/blue colours. This colour comes from
the electroplating which is the last manufacturing process. The
electroplated overlay has copper as one part of its composition, which
tarnishes to the dark colours described above. This tarnish colouration
has negligible thickness, so once installed in the engine, the crankshaft
journal contacting the bearing, will polish the bearing surface, removing
the surface colour and leaving the bearings with a polished silver
appearance.
Performance bearings do not start out with the silver grey appearance
of regular aftermarket bearings, as there is no final silvery tin flash
applied to these bearings. Not applying a silvery tin flash to these high
performance bearings is a specific design feature. A silvery tin flash
for appearance and long term corrosion protection, as applied to the
regular aftermarket bearings, can under high loading and heat, move,
with the plate migrating and causing high spots on the back of the
shells, and distorting the bearing. For this reason the ACL RACE Series
performance bearings do not have a cosmetic silvery tin flash applied,
so there is no risk of any overlay plate movement on the backs of the
shells, giving better bearing to housing contact and better bearing
performance and function.


Thanks for the input everybody.

Sir,

It looks like whatever part you showed, either the beam or cap, the appearance looks like it has not been dressed. The markings you are getting are somewhat typical of excessive crush across the parting line. Typically with newly resized rods, the parting faces will be very shiny. The one pictured still look like it has some dark wear markings.

The beam and caps are dressed to make the vertical length smaller and the bore then honed back round to size. Typically rods get smaller across the parting line, which could be the interference markings you have seen on the bearing. Honing brings both the vertical and parting dimensions back to size.

Plastigage should only be used to measure the vertical clearance between the bearing and the crank journal. When measuring the clearance with a bore gage this is also the only dimension that needs to be measured. Bearings will have some eccentricity built into them across the parting line, which is the reason why this dimension is not measured when checking for clearance.

You need to remove the bearing shell and retorque the rod together with the correct bolt stretch. With your new bore gauge measure the BE bore and make sure it is to the correct dimension. Not sure what rod you have but the sizes are well documented. Measure both the vertical dimension and across the parting line. The rod bore needs to be round, hopefully - 0.0000" / + 0.0001". Be careful here, the specs are a size tolerance that the bore can be, but the bore needs to be within 0.0001' whatever size you choose within that tolerance.

Then re fit the bearing shell making sure the backside of the bearing is clean. Then measure only the vertical dimension. This is the clearance.

Have a close inspection of the bearing shells where the tang is formed. Often I have seen the forming of the tang poorly done and the inside of the shell is pushed out as well.

Good luck.

Here are some additional photos that might show the machining better... I think the dark parts that you guys were seeing was possibly a reflection. Without having the rods with me - these appear to be much shinier in the pics i took on the weekend:

https://lh3.googleusercontent.com/m6...s=w687-h914-no

https://lh3.googleusercontent.com/1H...w=w687-h914-no

https://lh3.googleusercontent.com/3s...=w1219-h914-no

https://lh3.googleusercontent.com/1k...U=w687-h914-no

Thanks for your advice Neil.
Just wondering - what's the best way to torque the bolts when the rods are not being installed on the crank? I'd imagine a vice, but I'm concerned i would do it incorrectly and deform the rod.

Those photos show the caps and beams dressed. The first one showed some dark spots that gave the impression they had not.

Normally a rod vice, but a normal vice as long as you use care. Soft jaws and make sure the cap is all the way against the beam, then hold beam and cap.


The markings in the last photo show you are losing the clearance there. Something's out of round or the bearing is held off the cap there for some reason.