Possible rebuild of an S54 in an E86 Z4M Coupe

[tlow98]

The mains look typical of what I've seen. Did you use all yellow main bearing shells?

Interesting that you mention that. I know BMW says to start with yellows, measure and assess/change from there.

Then Lang says they start with green and adjust in either direction from there.

Not a lot of knowledge has been printed out here on the webs with personal experience. What are your thoughts on this?

my crank had a lot of green markings, and then it was pretty hard to tell the difference between the white/yellow markings with the oil patina over time.

[grannyknot]

The mains look typical of what I've seen. Did you use all yellow main bearing shells?

Good question, they weren't BMW, I'll have to have a look at the order.

[bigjae46]

Just to close off this thread, here are the pics of the conrod and main bearings when it was torn down, not bad shape at all but it was worth checking.

The mains look typical of what I've seen. Did you use all yellow main bearing shells?

[grannyknot]

Just to close off this thread, here are the pics of the conrod and main bearings when it was torn down, not bad shape at all but it was worth checking.

[bigjae46]

I haven’t ever heard of an S54 having main bearing issues. All of the mains I’ve pulled from S54s look like dull silver with some spotting.

Same thing with rings. Haven’t seen or heard or a piston ring going bad.


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[grannyknot]

Thanks guys, that's what I was thinking too but needed to hear it from someone else.

[cobra]

I wouldn't consider any of the routine maintenance items to include pistons and rings as a "while you're in there" since the head shouldn't have to come off...

These engines don't typically burn oil. I would just replace the 100k mile stuff and drive it.

[maupineda]

Leave the pistons and rings alone, a bad Job there would leave you in a worse place. Rod bearings and wearable items you feel like changing and your are good to go

[grannyknot]

Hi guys,
Hopping I can ask some advice from the engine builders here.
The car is an E86 Z4M coupe, 91,000mi on the S54 B32 engine, just bought the car last Oct. with almost no history. It appears to have been well cared for but I would like to start from a known baseline so will be replacing all wearable items.
The engine pulls well and sounds healthy, the compression numbers are good so I'm not worried about the pistons and rings. I don't know if it uses oil yet as I haven't driven the car much.
However, I don't know anything about the condition of the conrod and main bearings so I think they need to be replaced.
I have also purchased all of the timing components to be replaced, water pump, thermostat, etc.

So here is the question, since I'm in there anyway, should I just have the cylinders and rings done as well or just leave well enough alone? I hate the thought of messing around with such good numbers.
I have rebuilt many engines before including an S54 from a 2001 M3 with spun conrod bearing so I'm comfortable with whatever I find.
Thanks