Tom, It's worth it to have 2 more. I just read the article , International 6.9 the IDI father of the powerstroke. And It's great with a breakdown of the complete internal components, head design and injection system. The article ends like this, The 10 production engines were built and tested on the dynamometer to verify the quality of the production process. Each engine was subject to 1,000 hours(approx)80,000 miles at FULL load, with no problems occuring.In addition, pre-production engines were placed in customer fleet trucks and subjected to varied to various conditions,drivers,and use.