Single Scored Liner - MBN Cat

Would almost have to be a bad injector or lack of proper lubrication.

 

I suppose you could rotate injectors….marking #5 to a chosen other hole (preferably the one with the worst looking cross hatch marks) and see if it scores that liner.
Piston oil cooler nozzle alignment is a ordinary culprit. Maybe try rotating # 5 injector with the nozzle……if the oil pan is off already anyway?

 

I appreciate all your input! They have made my life miserable...

Both times when my truck was done and running there was no miss, engine was running perfectly fine when idle.

After thinking back, I suspect it can't be a bad injector do to a fact that for first 60 - 100 miles was running great.

I'm trying to eliminate things so j can get to a bottom of this.

I left a truck in Cali and took a plane home. I will be in touch with a shop and post the progress here.
Yesterday when I left they were sure that oil cooling jets were fine and that they checked one by one. I'm not sure if they honestly did it. It's a small shop.

If there was a cloggage in a block, could it effect only one piston?
Also, is it possible that the oil cooling jet is not getting anough oil/pressure?

Oil pump was replaced the first time and my pressure was good around 38pci idle and 70pci running.

 

3406E keeps scoring pistons

 

This is not my first overhaul. I did one on this engine and there wasn't any issue, i also have 6nz c15 that I did compile and no issues.

 

Well sounds like you have all the answers already then. Good luck