OK, so here's my saga. I filled my 2008 R55S with 87 octane Shell. Normally not an issue if you're not running at full boost, right? Well stupid me forgot and got into a 'Take no prisoners' combat mode situation. 10 minutes into it #3 piston was having no part of the foolihness and decided to depart, laving the battlefield to her 3 sisters. So a full set of piston, rings, standard sized con rod bearings, screws, etc went in and all should have been honky-dory. Had substantial difficulty...impossible actually.. rotating the crank. Naturally I attributed this to my practice of using white lithium on crank jouirnals. Removed rod caps, flushed bearings & journals then proceed to use Mobil1 0-50 as pre-lube. After re-assembly engine fired right off, running fine, making no odd or rude sounds. About 2 minutes running time I thought I heard a light tap when lightly bringing revs up 22-2800 revs...sounding like a classis con-rod knock to my ear. Hmmm..odd that since journals were as perfect could be and oe bearings were as new. Before installation I compared bearing sizes and overall dimensions, but not thickness. I mean, why would I...they were new and marked with STD,

Stethescope provided no help in isolating or locating the double light rap/knock. Un plugging #1 coil eliminated all knocking, confirmining my intiuition. Drained oil came out as clean as it went in. Removed sump, popped #1 rod cap and found bearing shells had rotated to 90 degree position..meaning split was at 12:00 and 18:00. OK, so I blamed myself for not securing shells in rod and cap securely. and installed another new pair of KING inserts on #1, and a new pair of rod cap screws. Fired her up as before...silent for 2-3 minutes..then the dreaded double tap/knock resurfaced, at the same rev range.

Sump came off again, oil looks clean and clear. When pulling #1 cap it seemed torque might have slipped a bit, but that may just have been my imagination at play. Again, sinsert retotated to the same 90 degree position. So, any ideas...like could it be the inserts are incorrectly sized due to them not being OE? Has anyone else encoutered a similar issue? Causes? Personally I've never ever seen a crank bearing without indexing tabs..an insane design. At the moment I'm giving serious thought to making several indexing marks in both rod and cap by means of a hardened punch, then applying a coating of LockTite red to those surfaces before re-assembly. Any remedies, solutions or thoughts anyone?

 

what is the torque spec you're applying?

did you make sure the mating surface with the bearings is dry and clean?

piston 3 was having issues but now it is fixed right, did you change its order to cyl 1 or each one returned to their original place?

Can you try and reuse the bearings of cyl 1?


in my case, the crankshaft would lock when use new bearings (in another installation it was fine though) so i reused the original bearing! the engine now runs fine.

 

Have you measured bearing clearance with plastigage?

 

This^

 

All rods were returned to their original cylinder position with new standard 'KING' bearings. New screws torqued per spec: 20 ft lbs + 90 degrees. I
Stupid me tossed the original inserts into the dumpster :(

 

I didn't use plastigage. I guess I'll have to this time around. Would you happen to have the specs?

 

This is what i followed when i did a bottom end swap on my '14 clubman.

https://www.newtis.info/tisv2/a/en/r...s-pins/5oXzVIU

 

Thanks for the link MiniToBe. New rod bearings were inserted and new screws torqued exactly as the link discribed. Two minutes of running produced the same double rap/knock/rattle at 2300-22900 revs. I'm thinking that the rod cap may have become slightly distorted/out of round. During initial assembly the upper shell slipped down, overlapping the cap insert. Unaware that this had occured, the screws were torqued. This faux-pas was discovered when trying to move the crank to do #'2 bearing. The crank journal and rod cap were checked closely as well as the bearing set. All appeared to be OK....although one of the inserts showed evidence of the overlap incident. A new pair of bearings were installed, and screws, and the rest as they say, is history.