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BMW E92 M3 bearing clearances

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Hi hope you are all well.

I am keen to purchase a V8 BMW M3 the S65 engine but understand it had drastically undersized bearing clearances from the manufacturer.

Is it possible to size bearing clearances with engine still in the car? I thought it might be possible with plastiguage but the measurable gap would be at the top of each shell so wouldn’t really work. I presume the crank has to come out unless any one knows another way?

my advise is dont take a short cut just do it right the first time remove the engine and measure it

Regards Ross

Same as what I was thinking Ross, sound advice only way to be truly sure. This really wasn’t the first thing I was hoping to do though! I see a lot of places offering to replace the bearings with new oem or fit different sized bearings but how can you be sure if you haven’t sized the clearance in the first place! Thanks for the reply.

Is it a known problem for your specific application? By that, I mean if you're stock or lightly modified and it is a problem for highly stressed engines, should you actually be worried?

Are you using the correct viscosity oil - a tighter clearance would suggest something like a 5-30, but some may be using a 20-50 (or even 60) viscosity oil in the mistaken belief that would give more protection, but actually be compromising the bearings by overheating because there isn't the oil passing through to remove the heat generated?

If the vehicle were new, it would be a warranty issue, and so a problem for BMW, but as it would seem it has some mileage on it, if it were a problem for your specific vehicle it would, presumedly, have shown up by now. The accumulated mileage will also have, potentially, increased the clearances slightly. You could ask if you could have an oil sample tested for bearing material?

Hi there, it is a known and well documented issue with the s65 engine machined from factory with bearing clearances about half the Industry minimum recognised standard. Engines have failed in all states of tune including standard from less than 6000 miles to over 70000. Oil samples are a common method used to track wear but not always guaranteed success at failure prevention.

Ah, thank you for the explanation. I have other issues with that brand, for all their "european cachet", in their domestic market they're the equivalent of a Ford or GM product. and as susceptible to design stuff-ups. On that, is that a model with the weld issue for the diff' mounting?