Injector washer thickness Cummins mechanical B series

[scenarioL113]

Hey guys, I can not get a straight answer. I have the Cummins manuals and I cant find the answer. I have mechanical 4BT (Cav pumps) 150hp version engines. I have been "dialing" these in all season and to be honest with you I did not take notice of the washer thickness for the Injectors when I did the initial rebuild. I put in the "medium" size and that is what is in them.

I feel like I am not hitting my mark at WOT (off by less than 100rpm) but not by much at all. (Both engines are within 10rpms of eachother)

I also noticed I am getting soot in the water on startup but not smoking, just a dry carbon floating on the surface (again BOTH engine).

I am running fine and my fuel consumption and cruise speed are excellent. I did 60 mile round trip last week and burned 25 -28 gallons of diesel (I am not complaining at all)

I am wondering if I am supposed to be running the "THIN" washers. After some research I found a few threads that mention the thin washers are more for marine and industrial applications...

My gut tells me that in my case the washers I am using are OK but I am usually wrong so if anyone has insight it would be very much appreciated.