Last Monday was in the shop getting some warranty work done on my differentials.
The guy who actually did my work had a paccar mx13 tore open replacing the #4 cylinder pack. Seems the paccar engine is showing the same habit of building carbon on the fire ring and piston like the isx Cummins.
They also have had two new X15 powered petercars in that had such major issues, they've had them at the shop going on 4 months and now Cummins is sending in acoustic engineers to locate the fault.
Neighbor has a 2005 isx turned up and deleted. His engine failed the same way. Carbon build up on fire rings and scored a cylinder.
Paccar and isx engines are two that I'd still avoid.
@Ranger_375 got a Volvo with the M13 engine or whatever it is the Volvo's got. He's been pretty good with it. Fuel mileage isn't what I'd have expected. Had some after treatment issues at first, but those seem to have been fixed when the EGR cooler got replaced. He has his engine set for 550/1850 I've been told.
@JunkYardDog5958 has run his classic with a 12.7 against it. He was impressed.
I run a Detroit 14L. Have about as few problems as I could expect out of it. Done an EGR delete and it's as rock solid and reliable as the 12.7 series 60. My second truck runs the 12.7 and fuel mileage is comparable between the two. Both are pulling beasts.
@JunkYardDog5958 has the 12.7 is set for 550/185 and my 14L is 630/2250.