Originally Posted by BMRLVR
I have pointed out what I think is the issue with the S65 "bearings" in a few threads now, but unfortunately someone at M3 post deleted posts as the discussions continued.
There is no major bearing issue with the S65. What the S65 has is oil clearances on the Main and Rod bearings that are in my opinion way too tight. For most engines there will most likely never be an issue, but, with clearances of around 0.001 there is not much room for error on assembly/during machining of the main bearing bores in the block. Basically what I am saying is that on an engine where the alignment of the main bearing bores is out even slightly or a rod has a big end that is even minutely oval shaped (either from manufacturing or by being stretched from an over-rev), there is no room for error at all. If the engine had say 0.002 which is a number that I feel should be a minimum, or even 0.0025 which the number I would like to see (TWS 10W60 is ideal to take advantage of this larger clearance since the viscosity of 60 at operating temp would lend you to believe it could handle a large oil clearance and oil pressure should not suffer) issues with the S65 main and rod "bearings" would be non existent.
So to all of you folks that think that the S65 has a rod bearing issue, that is not in any way shape of form the case, the S65 has a oil clearance issue and unless that is addressed no bearing you put into this engine will solve the problem unless the machine work is done to set the clearances to an acceptable number!
Exactly right. Similar issue with the S54, the clearances are so tight and manufacturing hiccup is a disaster waiting to happen. This is one of those issues where if it doesn't happen under warranty then it won't happen.
I also think that the S65 will have a similar life expectancy of the rod bearings when compared to the S54 ...100k miles. According to a BMW Master Tech...100k miles is about the average life of S54 rod bearings. I plan on doing preventive replacement on my S65 at 100k. I'm guessing blocks and cranks will be scarce and expensive.
I've felt the pain of spinning 3 bearings on my E46 M3.