Cummins has used their customers to ' de - bug ' engines before. In the late 1980's Cummins developed their L 10 series of inline 6 cylinder truck engines as an economical, fuel efficient fleet engine. My employer at the time, Conway Western, spec'ed a 300 H.P. L-10 in their Ford LN - Series Class 8 line tractors for 2 years. Many of these engines ran great for 150,000 miles or so, then the problems began. Cracked cylinder heads ( only one head for all 6 cylinders ) and cracked blocks were the 2 biggest issues; one tractor at my home yard went through THREE engine blocks in only 3 years / 300,000 miles. When the block would suddenly crack, all the coolant would dump out, causing engine shutdown & a few seizures and an expensive towing bill.
Several thoughts here: 1) The L 10 engine used 10 Liters ( about 600 Cubic Inches ) to make up to 350 H.P., while the Cummins NTC engine used 855 cubic inches for horsepower ratings up to 425. 2) Cummins did admit to problems with their casting techniques. ( duh ) 3) Cummins did repair and / or replace all affected engines for free, including the same engines bought by parent company Consolidated Freightways. 4) Cummins' warranty actions did little good, as CF & the Conways switched to the Caterpillar 3406 engine, ( one of the best truck engines ever IMO ), and refused to buy Cummins engines again ( except in yard goats ) for many years afterwards.
One other thought : When Amtrak began having problems with their CAT HEP engines in the F-59's, the local CAT Engine rep in Puget Sound ( Pape' Equipment ) was able to replace them on the Union Pacific Railroad spur next to their facility in Tukwila. I recall GE did warranty repairs on a siding in Anaheim on the P-42's as well ???