[MHDBMW12]

Hi, I replaced my rod bearings. Everything went well however I noticed one of the rod caps did not sit completely flush, the rest are perfect. I torqued it down correctly aswell. I have attached two pictures of the one sitting incorrectly. One picture of one that is perfect. Please help! I’m trying to finish this job asap.

[fastboatster]

might have switched the rod cap orientation and/or the upper bearing shell didn't get seated all the way in before you tightened the rod bolts down.

[MHDBMW12]

Originally Posted by fastboatster

might have switched the rod cap orientation and/or the upper bearing shell didn't get seated all the way in before you tightened the rod bolts down.

I’ll try reseating the bearing thanks, the cap is definitely in the correct orientation I double checked and I had marks when I put it in.

[fastboatster]

Originally Posted by MHDBMW12

I’ll try reseating the bearing thanks, the cap is definitely in the correct orientation I double checked and I had marks when I put it in.

probably bearings, then. make sure that locating tangs didn't get squashed or deformed.

[MHDBMW12]

Originally Posted by fastboatster

probably bearings, then. make sure that locating tangs didn't get squashed or deformed.

I reseated the bearings and inspected them, even switched them out with bearings from another cylinder and by playing around I was able to get it slightly better but still not perfect like the other cylinders. I’m not sure what to do at this point.

[fastboatster]

Does it become like a “one piece” when you tighten the bolts without bearings? Did you tighten it all the way (I.e., 20+90deg+90deg) when you saw it misaligned first? Was it initially like that or only after you got the new bearing shells? It might be possible that after you tighten it slightly offset, split surfaces no longer match each other 100%, some “peaks” got squashed and slightly widened no longer fitting corresponding “valleys”. You might need another rod in the worst case scenario.

[MHDBMW12]

I got it close but still not perfect even without the bearing shells. I did tighten it all the way before and I just noticed it misaligned as I was putting the pan on. I don’t remember if it was like that before touching it. Heres a couple pictures. I’m assuming close enough isn’t good enough. The engine is out of the car and I do have rods from another engine but I’d rather not take it apart. Would I have to get the head machined if I removed it ?

[Brandoch]

Did you had fully tightened up the rod bolts while the cap is not seated correctly? If so, you may have damaged the matting surfaces requiring a new connecting rod. I believe that these are cracked forged rods, meaning that the mating surfaces are very rough but they mate perfectly with as a set. If you did not align the cap perfectly with the rod and then tightened down, you most likely damaged the mating surfaces.

[MHDBMW12]

I think I may have, is it possible to take a rod from another engine and use it?i have an n54 for parts the rods are good.

[Brandoch]

Originally Posted by MHDBMW12

I think I may have, is it possible to take a rod from another engine and use it?i have an n54 for parts the rods are good.

Yes but you will have to take the head off to replace it. And measure the clearances for the rod bearing since you are changing the connecting rod.

[MHDBMW12]

Yes of course. Would the head have to be machined or would a new gasket be sufficient?

[fastboatster]

Originally Posted by MHDBMW12

Yes of course. Would the head have to be machined or would a new gasket be sufficient?

Probably just needs to be cleaned and then the new gasket would be enough. I wonder if it’s possible to pull the rod and piston down enough that the wrist pin and its circlips can be removed so that you can remove the old rod and put another one in. Probably not enough space to get the circlip pliers in place, but you never know.
P.S. don’t put an N54 rod in, it’s different from the n55 rods and probably has a significantly different weight

[MHDBMW12]

I was thinking that too but having the engine on the stand (it is a used engine). It might be good to take a look inside the cylinder anyways. My rod is from a newer N54 09 this is an 08 it should still be okay?

[fastboatster]

Originally Posted by MHDBMW12

I was thinking that too but having the engine on the stand (it is a used engine). It might be good to take a look inside the cylinder anyways. My rod is from a newer N54 09 this is an 08 it should still be okay?

as far as I know, late n54 rods are the same as early n54 rods, and all the n54 rods are different from the n55 rods. now with the n55 rods, there were early n55 rods (e series) which are not the same as f series ewg n55 rods even though e series rods got superseded by the ewg f series rods. I'm saying that you'll either need to get an early style e-series rod, or a complete set if you get it from a newer n55. Or I actually might not be quite right and you will need a complete set in either case.

[MHDBMW12]

I discovered an old thread where someone did essentially the same thing. Would It be worth changing out the piston rings ? The engine has 180k kms on it.

[MHDBMW12]

Would the washers for the cylinder head bolts also need to be changed or just the bolts?