Combines Engine slow down kit

A kit for that purpose doesn't exist. SDman posted an excellent answer (as usual!) to a similar question on Machinery Talk (Agriculture.com) yesterday. The bottom line is that the PTO and pump drive (and almost all other moving parts) is set up to work with 2700 rpm motor. Changing the motor rpm to 2200 would require replacement of the gearing on those parts, plus a host of other stuff to make your separator components run at the proper speed. If you are concerned about it, maybe look for a 1666. It would address this concern, plus give you other enhancements (new fan, etc.) My .02

If it like our experience, the earlier cummins running faster will use about 2_3 the fuel that the newer ones do. I certainly do not think it an issue. Just had to oh one of our IH 436's this winter '78 olde timer and crank checked out very good , over 5000hrs and never opened up, (OH because of cavitation of a sleeve) these ole gals runs 2700 just like early cummins. Our 21 series burns the most fuel.