M915A1 engine choices

Some of the M915A1 trucks I see have a Cummins Recon engine in them, CPL 891, as well as a Recon air compressor and Recon fuel pump. Others have a non-recon engine with CPL 531. My question is, when these trucks were rebuilt in the mid-2000s, did the 531s get an overhaul or just a coat of black paint?

CPL 891 was a Cummins ReCon CPL. It was generated because in order to update the 531 and a bunch of other 400HP engines, like the 614 MVT engine, it needed to be EPA certified. The 891 is just the updated older CPL. Things updated were piston dome, ring pack and placement of the ring set on the piston, compression and timing change for NoX, fuel mapping, etc.

The ReCon engine came complete, compressor, turbo, lube pump, injectors, all the components that make it an engine. The only parts that needed swapping were things like sensors/senders, fan hubs, flywheel housings. Anything "special" that the chassis maker added/needed to make it fit/work in their chassis.

If the engine data tag does not say ReCon and CPL891, it is an overhaul done in house or by someone else. The ReCon engines I saw were both black or beige.

I know on most any other engine that was overhauled by the military, there is a data tag on the engine that states the size of the crank journals and bore. I do not know ,if on the 855s that were overhauled by the military, that the engine has this tag.

915A1s went through numerous RESETs, IRONs, etc over their long career. It is my belief that the 400s were evaluated individually and either “painted black” or sent to Cummins for overhaul as determined necessary by the depot.