[DG330]

Hi,

So I think I might have early rod knock on my 320i xdrive. 100k+ miles.

Facts:

Slight knock on acceleration from 1500-3000rpm when halfway to operating temp upwards. No noise when cold.
Noise can be heard from under car by rear of the engine.
It can be heard in the rear of sump using a borescope
No oil pressure issues
Timing chains replaced over year ago.
Oil is a little shiny in oil filter housing.

Questions I need help with:

1. I am going to drop my oil and see the state of it. Given a timing change change, should I expect a little shine?

2. Anyone done this, how hard is it? The only bit concerning is either dropping the subframe or lifting the engine off the mounts enough to get the sump and front diff out.

3. Bearings suggestions? I am looking at either King race or ACL racing series. Maybe BMW ones, but it seems overly complicated with the B and R codes.

4. Anyone have the tolerances for plastiguage? PG-1 is the right one?


As I think this is early on I am hoping there is no damage to the crank, but I'll know when in there. If so I may hand polish it to smooth it.

Thoughts?

[DG330]

Bump bump

Thoughts on rod bearings?

Tempted to go for bmw, but it's annoying you have to wait until you're by the crank to know which ones you need.

I've heard that race bearings are normally on the lose side? Therefore would I need to run 5-40 rather than my 0-30.

[ScottSmith]

I was hoping to see some replies too, but not a lot of people building engines here. Tag navardi
Maybe try an N55 or S55 forum? Parts are the same anyways :-P

Answers to questions you didn't ask: Make sure you have the oil pump alignment tool, and either buy replacement stock rod bolts or get ARP. Though if you suspect rod knock, you may want to open it up first before assuming it's easily fixable... in which case ordering the stock B/R coded rod bearings isn't a burden (other than the higher cost compared to King/ACL).

[DG330]

Bump bump....

After thoughts on this, if I do go ahead with this I'll use genuine bearings, as I would be using genuine other parts too.

My only thought is whether the metal I am seeing in the oil is from the new timing chains? The metal I have is tiny flecks, so small that you only pick it up with a torch. You do see some silvery trails if you move the oil around.

Oil pressure wise, it seems to be very good comparing it against averages and a video online. Never seen an oil pressure light

[navardi]

So, Rod knock.... That's caused by poor oil pressure.
N20s share parts with the S55/N55, ACL offers racing bearings
King offers rebranded OEM or Rebranded ACL bearings.

Given your purpose you won't see a benefit from upgraded bearings but going with ACL would be the way to go, just you need to get tolerances measured by the engine shop.

However if you have rod knock, then there is more than likely further damage elsewhere or on the crank.

[DG330]

Originally Posted by navardi

So, Rod knock.... That's caused by poor oil pressure.
N20s share parts with the S55/N55, ACL offers racing bearings
King offers rebranded OEM or Rebranded ACL bearings.

Given your purpose you won't see a benefit from upgraded bearings but going with ACL would be the way to go, just you need to get tolerances measured by the engine shop.

However if you have rod knock, then there is more than likely further damage elsewhere or on the crank.

You think rod knock?

I'm going to change the oil and take a look at it.

If I change the bearings I'll be doing it and will use plastiguage, but what are the tolerances?