The number one cylinder has always been the one to show wear in our Cummins Diesels. And this is a history that spans 50 years and as many as 20 trucks running at a time. We have always attributed it to the fact the number one cylinder is the last to get oil. If bearings and cam bushings start getting excessive clearance, the no one just doesn't get enough oil. We recently lost a N14 due to a run away and it was the number one rod that spun. I also have an ISM in the shop right now that is a high miler and it is the number one that is low compression due to blowby. We didn't bother to mike the bore because we installed 6 piston packs that come with wet sleeves. No engineer has ever told me that this is the reason, but all of the old time mechanics that I have known over the past 60 years pretty much shared the theory.
