N14 Spun Rod Bearing

I buy new cranks for an n14 or Detroit for 2k. Not reman or reconditioned. I am the shop we do this sort of thing everyday. Oil pump is in the front and oil to the rear is least and hottest just like coolant. I agree with bearing roll in at 500k cheap insurance as has been said before but everyone is different. To this point I have never had a truck spin a bearing. We are Inframing one of our Petes with an n14 with 1.2 million and we rolled bearing when we bought it at 700k and other than starting to leak oil seemed like everywhere it was running good. Any questions on this build feel free to ask I have every manual you could ask for and like I said we do them on a daily basis, have an n14 down to the block as we speak for two main bearings seizing, at least one and the other was right behind it.

 

I have only had 2 N14 spin bearings out of close to 100 I worked on . One spun no6 main also due to block/cap fretting. The second was due to the oil pump. The pump shaft is not keyed to the drive gear in the pump, press fit only. This truck would have the occasional low oil light come on, always at idle and 100+miles away. One day it would not hold oil pressure unless it was at 800/1000 rpm. Customer was trying to make it to the shop. Acar pulled out in front of him and he let off of it, and seized two rod bearings.
I was able to salvage the crank, and had it running again before we figured out what caused it.

I still say probably 99% of bearing replacement is not necessary. Failure is usually due to underlying circumstances.

 

Pardon my ignorance, but could someone please define block fretting for me?

Thanks

 

The main caps will vibrate and wear some of the surface material off the block or the cap and close the tolerance between the bearing and the crank. It's not a vibration you can see or feel just micro vibrations. When it gets to close of a tolerance it will seize the crank inside the main journal. That's the reason for plastic gauging the bearing to crank tolerance is so important on an n14 and any engine really. There's a service bulletin from cummins saying use some sort of loctite when you install the caps to help mitigate the fretting.

 

Thanks Cory, that makes sense.