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      09-26-2012, 12:39 PM   #44

Drives: F10 M5
Join Date: Oct 2009
Location: NYC

iTrader: (1)

Originally Posted by BMRLVR View Post
The issue is most likely the fact that the engines are assembled too tight, i.e.: The main bearing oil clearance is insufficient. I would highly doubt that there is a deflection issue since the bedplate looks to be a very robust and rigid piece...... Much more rigid than what individual main caps would be.

The bearings in the pictures, although worn, are not excessively worn and definitely would not be causing significant oil pressure loss and definitely not be causing the ticking noise that many people are claiming is main bearings. The top layer of babbit is not even completely worn through but is polished quite a bit. When bearings are excessively worn they show the copper/bronze layer and many times have quite a bit of grooving and or discolouration due to heat. The whole purpose of the babbit layer on a bearing is for it to be able to touch the journal and/or to absorb contamination and do no damage to the journal in the process.

Another thing that may indeed cause bearing wear to these engines (or any engine for that matter) is high load before the engine oil is up to temperature. In my personal vehicles, I never use high throttle openings or place high load on my engines before the oil is at operating temperature, especially my M3! Even after the variable redline allows you the full 8400RPM I don't feel the oil is yet warm enough, personally I like to see my oil at around 85-90 degrees Celcius (185-195 degrees Fahrenheit) before I attempt any high load or high RPM. Any engine of ours that is required to be started and put at full load immediately (Back-Up Power, Pumps, or Emergency Vehicles) have engine heaters on them that keep the fluids (oil and coolant) at operating temp 24/7

The engine in the pictures would have lasted a long time before having any issues, and quite frankly, that wear may have occurred early in it's life and no further wear would have likely occurred once the clearance it needed was achieved. Any
Great post! Always love your inputs on stuff like this.

Anyways, my car never made a single sound up until a few months after I put the blower on. It got pretty noticeable a few months in, I just recently took the blower off and the sound is still present, but it seems to be very very faint (not as loud of a ticking). This is extremely weird, for if the ticking was a bearing issue wouldnt it make the same noise all the time in direct correlation with the crank? Could it be related to the stress on the motor as well? Meaning for example after doing 5 consecutive 60-130 pulls with 8lbs of boost in the motor it would tick alot louder than when I just drive around now naturally aspirated. At first when I got the car back I didnt hear any sounds so I thought the ticking had to do with the blower, but then the past few days I've been paying very close attention and the sound still is there, but nowhere near as loud or prominent. Does this make any sense? To me it doesn't, because a bearing on its way out would make the same noise all the time, but you obviously know alot more than me so I figured I'd ask..

Last edited by erm324; 09-26-2012 at 12:45 PM.