So I finally figured out what was causing a bit of engine pulsation and faint thumping after engine was fully warm.
Please note that this unit did not spin and crank neck had absolutely no scoring, while plastigaging at .05mm gap. Go figure what happened here

 

I'm no expert but it seems you are missing some grey metal on one set of bearings. It's that right, and we are not looking at the grub like item on one shell. As others look ok, was there an oiling issue or was this beating way to tight originally?

Engine is out of car I presume.

 

maybe the bottom end is not as tough as we believe! for the Jag V12, and they were known for oiling problems anyway.

did the engine ever have any head gasket problems?

wonder what its been thru in its life time.


looks like the crank pin is OK,check and measure carefully.

 

I think I would go with too tight a clearance to begin with. Seems if it were a oiling problem, they would all look like there was a oiling problem.

 

How many miles? Have the bearings ever been replaced before that you know of? Service history?

Just wondering.

You've got a couple others that aren't that far behind the worst example.

Cheers
DD

 

As far as I can tell, car was never overheated. Engine always ran very well and compression is all within 10% difference.
Mileage is around 100K, but for '82 only god knows if this is first, or second round.
Oil pressure was very good, around 25psi, hot @ 700 rpm, but now it is about 32psi.
Since plastigage showed .05mm clearance with new bearing, I decided not to investigate any further, but simply replace all bearings (main and rod). BTW, rod bearings were in excellent shape, only few were showing some pink.
I suppose this could be attributed to failed O2 sensor at some point, because disconnection of those causes my car to detonate, like it has an engine knock.


Right now I am building my spare engine, so all gray bearings are going to be combined with other gray bearings from that motor, to build me a spare.

 

Almost forgot, I read somewhere (maybe Kirbi Palm's book) that these motors are known for very strong cranks, but also for being rough on bearings, so it is not unheard of when bearings look like this, while not being spun and crank being perfectly undamaged. I have not found a single scoring on the entire crank.