600 hp

My rig has the ISX 525 Cummings engine which I bought before learning of the intake valve issue. My take on this is the higher the horsepower the sooner the acid from the EGR eats the face of the intake valves with number 6 being the first to go. Why #6 is first… maybe because it’s lower (engine is not mounted level) and the acid settles there (engine off). OTR trucks rarely have this problem as they do not sit unused for months at a time. This is my educated guess of what’s going on.
The fix appears to be new intake valves made out of better metal that resist the acid. $25,000 if you put the “new and improved” head on before it trashes the turbo and possibly the pistons.