Cat C15-6nz pinging sound rough idle

I had a similar issue like this on a C13 some years back. It ran and pulled fine, but after sitting and idling awhile and would "load up" and pop and smoke when getting moving again then would clear up and run fine. Eventually like every single C-13 I have been around, head gasket began to leak and I overhauled it. I try to to be thorough and I do pull cam followers apart and inspect and also pull rockers apart and inspect. What I found was rocker shaft wear on #5 and bushing ate up on injector rocker. I will attach the procedure on replacing the bushings on 3406E/C-15/C15, but it is best to let a machine shop do this or just buy new. The bushing needs to be sized after installed and Cat recommends chilling the pin to -80 F when pressing in. Driver did let me know that after overhauling that it never ran better and it never "loaded up" again. My only theory on the correlation of the two is the excessive wear actually lowers or delays the injected pressure enough it affects fuel atomization and timing in idle situation. As long as your block was cut correctly, I wouldn't think you will have wear at block and shouldn't need machining. I would check for sure though! Whichever way you go, make sure your pistons and injectors match and your tuning matches your injector. Compare your bowls when you pull and you will see the 18:1 vs 16:1 style have different size bowl diameters. Fuel needs to spray in the bowl and if the run nozzles designed for a different bowl you are spraying on the piston tops or even worse on the liners. Best to have head checked when off, lot easier then. Make the most of the unwanted downtime, you only want to do this once.

 

Don't know where you are but if you're going to play around with very expensive engines I would recommend taking it to a place that knows how to handle performance type work. Take it to Antrim Diesel in Greencastle PA. They know what they're doing and certainly would have put the right pistons in from the jump.