I removed the oil pan to have a look at the big end bearing on cylinder 3 and check the end float (I was worried about piston slap.)
No metal shavings or anything shiny looking.
I wiggled all of the other big ends while I was at it, and number 4 also moved a bit more than the others, although checking with a feeler still under .3mm. It's an L28 block.
So I removed number 4 and noticed that the bearing had a groove down the middle unlike number 3.
From pictures in the manual, I know that main bearings have that groove and big end bearings are smooth.
Would this cause an issue? 

Side note: It was a blown exhaust manifold gasket causing the noise on cylinder 3 that had me worried.

If I remember right that groove is an oiling feature.

 

 

https://www.google.com/search?q=crankshaft+bearings+classiczcars.com&client=ms-android-americamovil-us-revc&prmd=vsin&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjkrM7ItJjyAhUjc98KHaQPCM8Q_AUoA3oECAIQAw&biw=320&bih=449&dpr=2.25#imgrc=xiJYkfGv9-2Z8M

  On 8/4/2021 at 10:24 PM, siteunseen said:

If I remember right that groove is an oiling feature.

Why I am a bit concerned is that it seems like a feature of the main bearings and not rod bearings.

Any product image I see of rod bearings show them smooth:

I'm sorry, I lost my bearings reading your post. Post a picture of it and let the other members give you some experiences they may have had.

No grooves

Brand new King bearings.

It always amazes me how durable and forgiving the L Series Motors are. I’ve pulled engines that have the wide main bearing inserts mixed up with the narrow main bearing journals etc., but to no detriment. My guess is that you’ve got a rod bearing on a main and ended up with the main bearing on number 4. If the engine runs good and no oddities like oil usage, leave it alone........unless you want to pull the motor and replace all the bearings, I’d run it like you stole it! The important bearing is the center thrust bearing......its hard to mix that one up LOL.

main journal is 55mm, rod journal is 50mm. I think it must be more or less impossible to install one in the other. 

Might have to replace it..

  On 8/5/2021 at 7:25 PM, DuckManNK said:

Might have to replace it..

What does the journal look like?

If I found a bearing that looked like that, I would pull all the caps off and have a look at them all.

 

Edited August 5, 20213 yr by Racer X

The journal looked fine. No scratches/gouges or discoloration. 

I've seen some goofy work also, but my FAVORITE one is from high school.  My buddy asked me to help rebuild a SBF. I got everything checked at the machine shop and told my friend to get the machine work done - mains and rod journals need to be cut.  He called after he had the motor back and I went to his house with all the parts.  He was in a panic.  His father wanted that damn car out of his garage.  NP, we'll have the motor back in and ready to roll today.

So I dropped in the mains and lowered the crank in place, but it wouldn't drop in - at all.  I checked the bearings.  Yep they were correct, .020.  Then I put a bearing shell on the crank main journal.  Uh oh.  Not gonna happen. 

Me: Mike, you did get the crank cut, right?  

Mike: Cut?

Me: Uh oh.

Mike goes inside to tell his dad the car would not be moving today.  bull****, I heard him holler.  Next thing I know, dad is in the garage with us with a roll of aluminum foil.  Here, he says, make shims to space out the bearing caps, and get that damned car out of my garage.

I ran away. No way was I gonna be near that motor when he started it.